Expression enhancing intron sequences

ABSTRACT

The invention relates to methods for the identification and use of introns with gene expression enhancing properties. The teaching of this invention enables the identification of introns causing intron-mediated enhancement (IME) of gene expression. The invention furthermore relates to recombinant expression construct and vectors comprising said IME-introns operably linked with a promoter sequence and a nucleic acid sequence. The present invention also relates to transgenic plants and plant cells transformed with these recombinant expression constructs or vectors, to cultures, parts or propagation material derived there from, and to the use of same for the preparation of foodstuffs, animal feeds, seed, pharmaceuticals or fine chemicals, to improve plant biomass, yield, or provide desirable phenotypes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/241,493 filed Sep. 23, 2011, which is a divisional application ofU.S. application Ser. No. 11/885,988 filed Apr. 3, 2008, which is anational stage application (under 35 U.S.C. §371) of PCT/EP2006/060513filed Mar. 7, 2006, which claims benefit to U.S. Provisional application60/659,482 filed Mar. 8, 2005. The entire contents of each of theseapplications are hereby incorporated by reference herein in theirentirety.

SUBMISSION OF SEQUENCE LISTING

The Sequence Listing associated with this application is filed inelectronic format via EFS-Web and hereby incorporated by reference intothe specification in its entirety. The name of the text file containingthe Sequence Listing is Sequence_Listing_(—)074021_(—)0148_(—)01. Thesize of the text file is 119 KB, and the text file was created on May 5,2014.

FIELD OF THE INVENTION

The invention relates to methods for the identification and use ofintrons with gene expression enhancing properties. The teaching of thisinvention enables the identification of introns causing intron-mediatedenhancement (IME) of gene expression. The invention furthermore relatesto recombinant expression construct and vectors comprising saidIME-introns operably linked with a promoter sequence and a nucleic acidsequence. The present invention also relates to transgenic plants andplant cells transformed with these recombinant expression constructs orvectors, to cultures, parts or propagation material derived there from,and to the use of same for the preparation of foodstuffs, animal feeds,seed, pharmaceuticals or fine chemicals, to improve plant biomass,yield, or provide desirable phenotypes.

BACKGROUND OF THE INVENTION

The aim of plant biotechnology is the generation of plants withadvantageous novel properties, such as pest and disease resistance,resistance to environmental stress (e.g., drought), improved qualities(e.g., high yield), or for the production of certain chemicals orpharmaceuticals. Appropriate gene expression rates play an importantrole in order to obtain the desired phenotypes. The gene expression rateis mainly modulated by the promoter, additional DNA sequence located inthe 5′ untranscribed and 5′ untranslated region and the terminatorsequences of a given gene. Promoters are the portion of DNA sequenceslocated at the 5′ end a gene which contains signals for RNA polymerasesto begin transcription so that a protein synthesis can then proceed.Regulatory DNA sequences positioned in the 5′ untranscribed regionmodulate gene expression in response to specific biotic (e.g. pathogeninfection) or abiotic (e.g. salt-, heat-, drought-stress) stimuli.Furthermore, other so called “enhancer” sequences have been identifiedthat elevate the expression level of nearby located genes in a positionand orientation independent manner.

Beside the elements located on the untranscribed regions of a gene (e.g.promoter, enhancer), it is documented in a broad range of organisms(e.g. nematodes, insects, mammals and plants) that some introns havegene expression enhancing properties. In plants, the inclusion of someintrons in gene constructs leads to increased mRNA and proteinaccumulation relative to constructs lacking the intron. This effect hasbeen termed “intron mediated enhancement” (IME) of gene expression(Mascarenhas et al., (1990) Plant Mol. Biol. 15:913-920). Introns knownto stimulate expression in plants have been identified in maize genes(e.g. tubA1, Adh1, Sh1, Ubi1 (Jeon et al. (2000) Plant Physiol.123:1005-1014; Callis et al. (1987) Genes Dev. 1:1183-1200; Vasil et al.(1989) Plant Physiol 91:1575-1579; Christiansen et al. (1992) Plant Mol.Biol. 18:675-689]) and in rice genes (e.g. salT, tpi [McElroy et al.(1990) Plant Cell 2: 163-171; Xu et al. (1994) Plant Physiol106:459-467]). Similarly, introns from dicotyledonous plant genes likethose from petunia (e.g. rbcS), potato (e.g. st-ls1) and fromArabidopsis thaliana (e.g. ubq3 and pat1) have been found to elevategene expression rates (Dean et al. (1989) Plant Cell 1:201-208; Leon etal. (1991) Plant Phyisiol. 95:968-972; Norris et al. (1993) Plant MolBiol 21:895-906; Rose and Last (1997) Plant J 11:455-464). It has beenshown that deletions or mutations within the splice sites of an intronreduce gene expression, indicating that splicing might be needed for IME(Mascarenhas et al. (1990) Plant Mol Biol 15:913-920; Clancy and Hannah(2002) Plant Physiol 130:918-929). However, that splicing per se is notrequired for a certain IME in dicotyledonous plants has been shown bypoint mutations within the splice sites of the pat1 gene from A.thaliana (Rose and Beliakoff (2000) Plant Physiol 122:535-542).

Enhancement of gene expression by introns is not a general phenomenonbecause some intron insertions into recombinant expression cassettesfail to enhance expression (e.g. introns from dicot genes (rbcS genefrom pea, phaseolin gene from bean and the stls-1 gene from Solanumtuberosum) and introns from maize genes (adh1 gene the ninth intron,hsp81 gene the first intron)) (Chee et al. (1986) Gene 41:47-57;Kuhlemeier et al. (1988) Mol Gen Genet. 212:405-411; Mascarenhas et al.(1990) Plant Mol Biol 15:913-920; Sinibaldi and Mettler (1992) In WECohn, K Moldave, eds, Progress in Nucleic Acid Research and MolecularBiology, Vol 42. Academic Press, New York, pp 229-257; Vancanneyt et al.1990 Mol Gen Gent 220:245-250). Therefore, not each intron can beemployed in order to manipulate the gene expression level of alien genesor endogenous genes in transgenic plants. What characteristics orspecific sequence features must be present in an intron sequence inorder to enhance the expression rate of a given gene is not known in theprior art and therefore from the prior art it is not possible to predictwhether a given plant intron, when used heterologously, will cause IME.

The introduction of a foreign gene into a new plant host does not alwaysresult in a high expression of the incoming gene. Furthermore, ifdealing with complex traits, it is sometimes necessary to modulateseveral genes with spatially or temporarily different expressionpattern. Introns can principally provide such modulation. Howevermultiple use of the same intron in one plant has shown to exhibitdisadvantages. In those cases it is necessary to have a collection ofbasic control elements for the construction of appropriate recombinantDNA elements. However, the available collection of introns withexpression enhancing properties is limited and alternatives are needed.

Thus, there is still a growing demand for basic control elementsincluding promoters, regulatory sequences (e.g., inducible elements,enhancers) or intron sequences that have an impact on gene expressionrates. It is therefore an objective of the present invention, to providea highly reproducible and reliable method for the identification ofintrons with expression enhancing properties.

This objective is achieved by the methods provided within thisinvention.

SUMMARY OF THE INVENTION

A first subject matter of the invention therefore relates to a methodfor identifying an intron with expression enhancing properties in plantscomprising selecting an intron from a plant genome, wherein said intronis characterized by at least the following features

-   I) an intron length shorter than 1,000 base pairs, and-   II) presence of a 5′ splice site comprising the dinucleotide    sequence 5′-GT-3′ (SEQ ID NO: 78), and-   III) presence of a 3′ splice site comprising the trinucleotide    sequence 5′-CAG-3′ (SEQ ID NO: 79), and-   IV) presence of a branch point resembling the consensus sequence    5′-CURAY-3′ (SEQ ID NO:75) upstream of the 3′ splice site, and-   V) an adenine plus thymine content of at least 40% over 100    nucleotides downstream from the 5′ splice site, and-   VI) an adenine plus thymine content of at least 50% over 100    nucleotides upstream from the 3′ splice site, and-   VII) an adenine plus thymine content of at least 50%, and a thymine    content of at least 30% over the entire intron.

In another embodiment, the invention relates to a method for enrichingthe number of introns with expression enhancing properties in plants ina population of plant introns to a percentage of at least 50% of saidpopulation, said method comprising selecting introns from saidpopulation, wherein said introns are characterized by at least thefollowing features

-   I) an intron length shorter than 1,000 base pairs, and-   II) presence of a 5′ splice site comprising the dinucleotide    sequence 5′-GT-3′ (SEQ ID NO: 78), and-   III) presence of a 3′ splice site comprising the trinucleotide    sequence 5′-CAG-3′ (SEQ ID NO: 79), and-   IV) presence of a branch point resembling the consensus sequence    5′-CURAY-3′ (SEQ ID NO:75) upstream of the 3′ splice site, and-   V) an adenine plus thymine content of at least 40% over 100    nucleotides downstream from the 5′ splice site, and-   VI) an adenine plus thymine content of at least 50% over 100    nucleotides upstream from the 3′ splice site, and-   VII) an adenine plus thymine content of at least 50%, and a thymine    content of at least 30% over the entire intron.

Preferably, the population of plant introns chosen for the enrichment ofintrons with gene expression enhancing properties in plants comprisessubstantially all introns of a plant genome represented in a genomic DNAsequence database or a plant genomic DNA library.

In a preferred embodiment, the intron with gene expression enhancingproperties in plants (“IME-intron”) is selected by the method of theinvention for identifying IME-introns or the method of the invention forenriching the number of IME-introns in a population of plant introns.Preferably, said intron is selected from the group consisting of intronslocated between two protein encoding exons or introns located within the5′ untranslated region of the corresponding gene.

In a particularly preferred embodiment, the IME-intron is identified orenriched by one of the inventive methods from a group or population ofgenes representing the 10% fraction of genes with the highest expressionrate in a gene expression analysis experiment performed using a plantcell, plant tissue or a whole plant.

The invention furthermore relates to a method wherein the gene sequenceinformation used for the identification or enrichment of IME-introns ispresent in a DNA sequence database and the selection steps foridentifying or enriching said introns are performed using an automatedprocess, preferably by using a computer device and an algorithm thatdefines the instructions needed for accomplishing the selection stepsfor identifying or enriching said introns.

Additionally, the invention relates to computer algorithm that definesthe instructions needed for accomplishing the selection steps foridentifying or enriching IME-introns from a plant genome or a populationof introns selected from the group consisting of introns located betweentwo protein encoding exons, and/or introns located within the 5′untranslated region of the corresponding gene and/or introns located inthe DNA sequences of genes representing the 10% fraction of genes withthe highest expression rate in a gene expression analysis experimentperformed using a plant cell, plant tissue and/or a whole plant.

The invention also relates to the computer device or data storage devicecomprising an algorithm as described above.

In a preferred embodiment, the invention relates to methods forisolating, providing or producing IME-introns comprising the steps ofperforming an identification or enrichment of IME-introns as describedabove and providing the sequence information of said IME-intronsidentified or enriched, and providing the physical nucleotide sequenceof said identified or enriched introns and evaluating the geneexpression enhancing properties of the isolated introns in an in vivo orin vitro expression experiment, and isolating the IME-introns from thepopulation of introns tested in the in vivo or in vitro expressionexperiment. Preferably, the evaluation of the gene expression enhancingproperties of the IME-intron is done in a plant cell and whereinIME-intron enhances the expression of a given nucleic acid at leasttwofold.

An additional subject matter of the invention relates to a recombinantDNA expression construct comprising at least one promoter sequencefunctioning in plants cells, at least one nucleic acid sequence and atleast one intron selected from the group consisting of the sequencesdescribed by SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21 and 22, and functional equivalents thereof, whereinsaid promoter sequence and at least one of said intron sequences arefunctionally linked to said nucleic acid sequence and wherein saidintron is heterologous to said nucleic acid sequence or to said promotersequence.

Furthermore, the invention relates to recombinant expression constructscomprising at least one promoter sequence functioning in plants cells,at least one nucleic acid sequence and at least one functionalequivalents of an intron described by any of sequences SEQ ID NOs: 1, 2,3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and 22,wherein said functional equivalent comprises the functional elements ofan intron and is characterized by

-   a) a sequence having at least 50 consecutive base pairs of the    intron sequence described by any of SEQ ID NOs: 1, 2, 3, 5, 6, 7,    10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22, or-   b) having an identity of at least 80% over a sequence of at least 95    consecutive nucleic acid base pairs to a sequences described by any    of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18,    19, 20, 21 or 22, or-   c) hybridizing under high stringent conditions with a nucleic acid    fragment of at least 50 consecutive base pairs of a nucleic acid    molecule described by any of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11,    12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22,

wherein said promoter sequence and at least one of said intron sequencesare functionally linked to said nucleic acid sequence and wherein saidintron is heterologous to said nucleic acid sequence or to said promotersequence.

In another embodiment, the recombinant DNA expression construct of theinvention further contains one or more additional regulatory sequencesfunctionally linked to promoter. Those regulatory sequences can beselected from the group consisting of heat shock responsive-, anaerobicresponsive-, pathogen responsive-, drought responsive-, low temperatureresponsive-, ABA responsive-elements, 5′ untranslated gene region, 3′untranslated gene region, transcription terminators, polyadenylationsignals and enhancers.

The nucleic acid sequence of the inventive recombinant DNA expressionconstruct may result in the expression of a protein and/or sense,antisense or double-stranded RNA encoded by said nucleic acid sequence.

In another embodiment, the nucleotide sequence encoding the transgenicexpression construct of the invention is double-stranded. In yet anotherembodiment, the nucleotide sequence encoding the transgenic expressionconstruct of the invention is single-stranded.

In yet another alternative embodiment of the invention, the recombinantexpression construct comprises a nucleic acid sequence encoding for aselectable marker protein, a screenable marker protein, a anabolicactive protein, a catabolic active protein, a biotic or abiotic stressresistance protein, a male sterility protein or a protein affectingplant agronomic characteristics.

The invention relates furthermore to vectors containing a transgenicexpression construct of the invention. Additionally, the inventionrelates to transgenic cells or transgenic non-human-organisms likebacteria, fungi, yeasts or plants comprising an expression vectorcontaining a transgenic expression construct of the invention. In apreferred embodiment, the transgenic cell or transgenic non-humanorganism transformed with an expression construct of the invention is amonocotyledonous plant or is derived from such a plant. In a yet morepreferred embodiment, the monocotyledonous plant is selected from thegroup consisting of the genera Hordeum, Avena, Secale, Triticum,Sorghum, Zea, Saccharum, and Oryza. Further embodiments of the inventionrelate to cell cultures, parts or propagation material derived fromnon-human-organisms like bacteria, fungi, yeasts and/or plants,preferably monocotyledonous plants, most preferably plants selected fromthe group consisting of the genera Hordeum, Avena, Secale, Triticum,Sorghum, Zea, Saccharum, and Oryza, transformed with the inventivevectors or containing the inventive recombinant expression constructs.

The invention furthermore relates to a method for providing anexpression cassette for enhanced expression of a nucleic acid sequencein a plant or a plant cell, comprising the step of functionally linkingat least one sequence selected from the group consisting of SEQ ID NOs:1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and 22to said nucleic acid sequence.

The invention further relates to a method for enhancing the expressionof a nucleic acid sequence in a plant or a plant cell, comprisingfunctionally linking at least one sequence selected from the groupconsisting of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21 and 22 to said nucleic acid sequence.

An additional embodiment of the invention relates to a method

-   a) for providing an expression cassette for enhanced expression of a    nucleic acid sequence in a plant or a plant cell, or-   b) for enhancing the expression of a nucleic acid sequence in a    plant or a plant cell said method comprising functionally linking at    least one sequence selected from the group consisting of SEQ ID NOs:    1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 and    22 to said nucleic acid sequence, wherein furthermore a promoter    sequence functional in plants is linked to said nucleic acid    sequence.

Preferably, at least one sequence selected from the group consisting ofSEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,20, 21 and 22 is linked to a nucleic acid sequence by insertion into theplant genome via homologous recombination. Preferably, said homologousrecombination is comprising at least the steps of

-   a) providing in vivo or in vitro a DNA construct comprising said    intron flanked by sequences (“recombination substrate”) allowing    homologous recombination into a pre-existing expression cassette    between the promoter and the nucleic acid of said expression    cassette, and-   b) transforming a recipient plant cell comprising said cassette of    step a) and regenerating a transgenic plant, wherein said intron has    been inserted into the genome of said plant. Preferably, the site of    integration into the genome of said plant is determined by the DNA    sequence of the recombination substrate of step a), wherein said    sequence sharing sufficient homology (as defined herein) with said    genomic target DNA sequence allowing the sequence specific    integration via homologous recombination at said genomic target DNA    locus.

In a preferred embodiment of the invention, said recipient plant orplant cell is a monocotyledonous plant or plant cell, more preferably aplant or plant cell selected from the group consisting of the generaHordeum, Avena, Secale, Triticum, Sorghum, Zea, Saccharum, and Oryza,most preferably a maize plant.

Preferably, the nucleic acid sequence to which one of the inventiveintron is functionally linked, encodes for a selectable marker protein,a screenable marker protein, an anabolic active protein, a catabolicactive protein, a biotic or abiotic stress resistance protein, a malesterility protein or a protein affecting plant agronomic characteristicsand/or a sense, antisense, or double-stranded RNA.

Additionally, the invention relate to the use of a transgenic organismof the invention or of cell cultures, parts of transgenic propagationmaterial derived there from for the production of foodstuffs, animalfeeds, seeds, pharmaceuticals or fine chemicals.

The invention furthermore relates to a recombinant DNA expressionconstruct comprising

-   a) at least one promoter sequence functioning in plants or plant    cells, and-   b) at least one intron selected from the group of introns with    expression enhancing properties in plants or plant cells    characterized by at least the following features    -   -   I) an intron length shorter than 1,000 base pairs, and        -   II) presence of a 5′ splice site comprising the dinucleotide            sequence 5′-GT-3′ (SEQ ID NO: 78), and        -   III) presence of a 3′ splice site comprising the            trinucleotide sequence 5′-CAG-3′ (SEQ ID NO: 79), and        -   IV) presence of a branch point resembling the consensus            sequence 5′-CURAY-3′ (SEQ ID NO: 75) upstream of the 3′            splice site, and        -   V) an adenine plus thymine content of at least 40% over 100            nucleotides downstream from the 5′ splice site, and        -   VI) an adenine plus thymine content of at least 50% over 100            nucleotides upstream from the 3′ splice site, and        -   VII) an adenine plus thymine content of at least 55%, and a            thymine content of at least 30% over the entire intron, and

at least one nucleic acid sequence, wherein said promoter sequence andat least one of said intron sequences are functionally linked to saidnucleic acid sequence and wherein said intron is heterologous to saidnucleic acid sequence and/or to said promoter sequence.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 Map of pBPSMM291 (SEQ ID NO: 109)

This vector comprises the maize ubiquitin promoter, followed by theBPSI.1, then the GUSint ORF (including the potato invertase [PIV]2intron to prevent bacterial expression), followed by nopaline synthase(NOS) terminator. This vector contains the attL1 and attL2 sites to makeit compatible with modification via the Gateway® cloning Technology fromInvitrogen™. This vector is based on the pUC based expression vectorpBPSMM267. The XmaI-RsrII digested BPSI.1 PCR product was ligated intothe XmaI-RsrII digested pBPSMM267 to create pBPSMM291. The vectorspBPSMM293, pBPSMM294 and pBPSMM295 have been created accordingly (seetable 6 and 1.6.1).

FIG. 2 Map of pBPSMM305 (SEQ ID NO:110)

The expression vector pBPSMM305 comprises the maize lactatedehydrogenase (LDH) promoter without intron driving expression of theGUSint ORF (including the potato invertase [PIV]2 intron to preventbacterial expression), followed by the NOS terminator. This vector hasbeen used to create the pUC based expression vectors pBPSJB041,pBPSJB042, pBPSJB043, pBPSJB044, pBPSJB045, pBPSJB046 and pBPSJB050 (seeexamples 2.3).

FIG. 3 Map of pBPSMM350 (SEQ ID NO:111):

The vector pBPSMM350 comprises the maize ubiquitin promoter, followed bythe BPSI.1, then the GUSint ORF (including the potato invertase [PIV]2intron to prevent bacterial expression), followed by nopaline synthase(NOS) terminator. The expression cassette has been transferred from thevector pBPSMM291 using the Gateway® cloning Technology from Invitrogen™.The vectors pBPSMM353, pBPSMM312 and pBPSMM310 have been createdaccordingly (see table 6 and example 1.6.2).

FIG. 4 Map of pBPSLM139 (SEQ ID NO:112):

The vector pBPSLM139 comprises the selectable marker expressioncassette. In order to produce the vectors pBPSLI017 to pBPSLI023,PmeI/PacI fragments have been isolated from the vectors pBPSJB-042,-043, -044, -045, 046 and 050 and cloned into the PmeI-PacI digestedpBPSLM130 (see example 2.3 and 2.4)

FIG. 5 a-f: Computer algorithm for retrieving sequence information fromNCBI genebank file.

FIG. 6 Transgenic plants containing promoter constructs with BPSI.1intron (all but pBPSLM229) or BPSI.5 intron (only pBPSLM229) were testedfor GUS expression at 5-leaf (A), flowering (B) and seed set (C) stages.Shown are examples of typical staining patterns obtained from at least15 independent events. All samples were stained for 16 hours in GUSsolution. Promoters in the constructs are: rice chloroplast protein 12(Os.CP12; pBPSMM355), the maize hydroxyproline-rich glycoprotein(Zm.HRGP; pBPSMM370), the rice p-caffeoyl-CoA 3-O-methyltransferase(Os.CCoAMT1; pBPSMM358), the maize Globulin-1 promoter W64A (Zm.Glb1;EXS1025), the putative Rice H+-transporting ATP synthase promoter(Os.V-ATPase; pBPSMM369), Zm.LDH (pBPSMM357), the rice C-8,7 sterolisomerase promoter (Os.C8,7 SI; pBPSMM366), the rice Late EmbryogenesisAbundant Protein promoter (Os.Lea; pBPSMM371), and the maize lactatedehydrogenase promoter (ZM.LDH; pBPSLM229).

GENERAL DEFINITIONS

It is to be understood that this invention is not limited to theparticular methodology, protocols, cell lines, plant species or genera,constructs, and reagents described as such It must be noted that as usedherein and in the appended claims, the singular forms “a” and “the”include plural reference unless the context clearly dictates otherwise.Thus, for example, reference to “a vector” is a reference to one or morevectors and includes equivalents thereof known to those skilled in theart.

About: the term “about” is used herein to mean approximately, roughly,around, or in the region of. When the term “about” is used inconjunction with a numerical range, it modifies that range by extendingthe boundaries above and below the numerical values set forth. Ingeneral, the term “about” is used herein to modify a numerical valueabove and below the stated value by a variance of 20 percent, preferably10 percent up or down (higher or lower). As used herein, the word “or”means any one member of a particular list.

Agrobacterium: refers to a soil-borne, Gram-negative, rod-shapedphytopathogenic bacterium which causes crown gall. The term“Agrobacterium” includes, but is not limited to, the strainsAgrobacterium tumefaciens, (which typically causes crown gall ininfected plants), and Agrobacterium rhizogenes (which causes hairy rootdisease in infected host plants). Infection of a plant cell withAgrobacterium generally results in the production of opines (e.g.,nopaline, agropine, octopine etc.) by the infected cell. Thus,Agrobacterium strains which cause production of nopaline (e.g., strainLBA4301, C58, A208) are referred to as “nopaline-type” Agrobacteria;Agrobacterium strains which cause production of octopine (e.g., strainLBA4404, Ach5, B6) are referred to as “octopine-type” Agrobacteria; andAgrobacterium strains which cause production of agropine (e.g., strainEHA105, EHA101, A281) are referred to as “agropine-type” Agrobacteria.

Algorithm: as used herein refers to the way computers processinformation, because a computer program is essentially an algorithm thattells the computer what specific steps to perform (in what specificorder) in order to carry out a specified task, such as identification ofcoding regions of a set of genes. Thus, an algorithm can be consideredto be any sequence of operations that can be performed by a computersystem. Typically, when an algorithm is associated with processinginformation, data is read from an input source or device, written to anoutput sink or device, and/or stored for further use. For any suchcomputational process, the algorithm must be rigorously defined:specified in the way it applies in all possible circumstances that couldarise. That is, any conditional steps must be systematically dealt with,case-by-case; the criteria for each case must be clear (and computable).Because an algorithm is a precise list of precise steps, the order ofcomputation will almost always be critical to the functioning of thealgorithm. Instructions are usually assumed to be listed explicitly, andare described as starting ‘from the top’ and going ‘down to the bottom’,an idea that is described more formally by flow of control. In computerapplications, a script is a computer program that automates the sort oftask that a user might otherwise do interactively at the keyboard.Languages that are largely used to write such scripts are calledscripting languages. Many such languages are quite sophisticated, andhave been used to write elaborate programs, which are often still calledscripts even if they go well beyond automating simple sequences of usertasks. Computer languages are created for varying purposes and tasksdifferent kinds and styles of programming. Scripting programminglanguages (commonly called scripting languages or script languages) arecomputer programming languages designed for “scripting” the operation ofa computer. Early script languages were often called batch languages orjob control languages.

Examples for script languages are: ACS, ActionScript, Active ServerPages (ASP), AppleScript, Awk, BeanShell (scripting for Java), bash,Brain, CobolScript, csh, ColdFusion, Dylan, Escapade (server sidescripting), Euphoria, Groovy, Guile, Haskell, HyperTalk, ICI, IRCscript, JavaScript, mIRC script, MS-DOS batch, Nwscript, Perl, PHP,Pike, ScriptBasic.

Antisense: is understood to mean a nucleic acid having a sequencecomplementary to a target sequence, for example a messenger RNA (mRNA)As used herein, the terms “complementary” or “complementarity” are usedin reference to nucleotide sequences related by the base-pairing rules.For example, the sequence 5′-AGT-3′ is complementary to the sequence5′-ACT-3′. Complementarity can be “partial” or “total.” “Partial”complementarity is where one or more nucleic acid bases is not matchedaccording to the base pairing rules. “Total” or “complete”complementarity between nucleic acids is where each and every nucleicacid base is matched with another base under the base pairing rules. Thedegree of complementarity between nucleic acid strands has significanteffects on the efficiency and strength of hybridization between nucleicacid strands.

Sense: is understood to mean a nucleic acid having a sequence that ishomologous or identical to a target sequence, for example a sequencewhich is bound by a protein factor of the spliceosome.

Bombarding, “bombardment and “biolistic bombardment”: refer to theprocess of accelerating particles (microprojectiles) towards a targetbiological sample (e.g., cell, tissue, etc.) to effect wounding of thecell membrane of a cell in the target biological sample and/or entry ofthe particles into the target biological sample. Methods for biolisticbombardment are known in the art (e.g., U.S. Pat. No. 5,584,807, thecontents of which are herein incorporated by reference), and arecommercially available (e.g., the helium gas-driven microprojectileaccelerator (PDS-1000/He) (BioRad).

Cell: refers to a single cell. The term “cells” refers to a populationof cells. The population may be a pure population comprising one celltype. Likewise, the population may comprise more than one cell type. Inthe present invention, there is no limit on the number of cell typesthat a cell population may comprise. The cells may be synchronize or notsynchronized, preferably the cells are synchronized.

Chromosomal DNA or chromosomal DNA-sequence: is to be understood as thegenomic DNA of the cellular nucleus independent from the cell cyclestatus. Chromosomal DNA might therefore be organized in chromosomes orchromatids, they might be condensed or uncoiled. An insertion into thechromosomal DNA can be demonstrated and analyzed by various methodsknown in the art like e.g., polymerase chain reaction (PCR) analysis,Southern blot analysis, fluorescence in situ hybridization (FISH), andin situ PCR.

Coding region or coding sequence (CDS): when used in reference to a generefers to the nucleotide sequences which encode the amino acids found inthe nascent polypeptide as a result of translation of a mRNA molecule.The coding region is bounded, in eucaryotes, on the 5′-side by thenucleotide triplet “ATG” which encodes the initiator methionine and onthe 3′-side by one of the three triplets, which specify stop codons(i.e., TAA, TAG, TGA).

Complement of a nucleic acid sequence: as used herein refers to anucleotide sequence whose nucleic acids show total complementarity tothe nucleic acids of the nucleic acid sequence.

Decile: when used in connection with statistical data is any of the 10values that divide sorted data into 10 equal parts, so that each partrepresents 1/10th of the sample or population. Thus, the 1st decile cutsoff lowest 10% of data, the 9th decile cuts off lowest 90% or thehighest 10% of data. A quartile is any of the three values which dividethe sorted data set into four equal parts, so that each part represents¼th of the sample or population (third quartile=upper quartile=cuts offhighest 25% of data, or lowest 75%=75th percentile). A percentile is anyof the 99 values that divide the sorted data into 100 equal parts, sothat each part represents 1/100th of the sample or population. Thus, the1st percentile cuts off lowest 1% of data, the 98th percentile cuts offlowest 98% of data and the 25^(th) percentile cuts off lowest 25% ofdata.

DNA databases: in the field of bioinformatics, a DNA sequence databaseis a large collection of DNA sequences stored on a computer. A databasecan include sequences from only one organism, or it can includesequences from all organisms whose DNA has been sequenced.

Enrichment or enriching: when used in connection with the selection ofinventive introns refers to an increase in the success rate ofidentifying introns with gene expression enhancing properties within apopulation of introns (e.g. a population of introns representing allintrons of a plant genome present in a genomic DNA sequence database).The enrichment is achieved by reducing the number of candidate intronsby using the inventive method and the inventive selection criteria. If,as an example, the success rate of identifying an intron with expressionenhancing properties from a given population of introns—by using theherein described methods for measuring gene expression enhancement—isone out of ten analyzed introns, enrichment has to be understood as anincrease in the number of identified introns with gene expressionenhancing properties—by using the inventive method- to at least five outof ten analyzed introns. Therefore, the number of introns needed to beanalyzed in order to identify one inventive intron is reduced to twointrons by using the inventive method as a preselection or filteringprocess.

Evaluation of the expression enhancing properties: of an intron can bedone using methods known in the art. For example, a candidate intronsequence whose gene expression enhancing effect is to be determined canbe inserted into the 5′UTR of a nucleic acid sequence encoding for areporter gene (e.g., a visible marker protein, a selectable markerprotein) under control of an appropriate promoter active in plants orplant cells to generate a reporter vector. The reporter vector and anidentical control reporter vector lacking the candidate intron can beintroduced into a plant tissue using methods described herein, and theexpression level of the reporter gene, in dependence of the presence ofthe candidate intron, can be measured and compared (e.g., detecting thepresence of encoded mRNA or encoded protein, or the activity of aprotein encoded by the reporter gene). An intron with expressionenhancing properties will result in a higher expression rate than areference value obtained with an identical control reporter vectorlacking the candidate intron under otherwise unchanged conditions.

The reporter gene may express visible markers. Reporter gene systemswhich express visible markers include β-glucuronidase and its substrate(X-Gluc), luciferase and its substrate (luciferin), and β-galactosidaseand its substrate (X-Gal) which are widely used not only to identifytransformants, but also to quantify the amount of transient or stableprotein expression attributable to a specific vector system (Rhodes(1995) Methods Mol Biol 55:121-131). The assay with β-glucuronidase(GUS) being very especially preferred (Jefferson et al., GUS fusions:beta-glucuronidase as a sensitive and versatile gene fusion marker inhigher plants. EMBO J. (1987) December 20; 6(13):3901-3907).β-glucuronidase (GUS) expression is detected by a blue color onincubation of the tissue with 5-bromo-4-chloro-3-indolyl-β-D-glucuronicacid. The selectable marker gene may confer antibiotic or herbicideresistance. Examples of reporter genes include, but are not limited to,the dhfr gene, which confers resistance to methotrexate (Wigler (1980)Proc Natl Acad Sci 77:3567-3570); npt, which confers resistance to theaminoglycosides neomycin and G-418 (Colbere-Garapin (1981) J. Mol. Biol.150:1-14) and als or pat, which confer resistance to chlorsulfuron andphosphinotricin acetyl transferase, respectively.

Expect value when used in the context of DNA sequence alignments or DNAsequence database searches refers to the number of times a certain matchor a better one would be expected to occur purely by chance in a searchof the entire database. Thus, the lower the Expect value, the greaterthe similarity between the input sequence and the match. The Expectvalue (E) is a parameter that describes the number of hits one can“expect” to see just by chance when searching a database of a particularsize. It decreases exponentially with the Similarity Score (S) that isassigned to a match between two sequences. The higher the score, thelower the E value. Essentially, the E value describes the randombackground noise that exists for matches between sequences. The Expectvalue is used as a convenient way to create a significance threshold forreporting results. An E value of 1 assigned to a hit can be interpretedas meaning that in a database of the current size you might expect tosee 1 match with a similar score simply by chance. The E-value isinfluenced by: a) length of sequence (the longer the query the lower theprobability that it will find a sequence in the database by chance), b)size of database (the larger the database the higher the probabilitythat the query will find a match by chance), c) the scoring matrix (theless stringent the scoring matrix the higher the probability that thequery will find a sequence in the database by chance).

Expressed sequence tag (EST): refers to a cDNA sequence that has beenobtained from a single pass terminal DNA sequencing. An EST sequencedenotes a sequence that is derived from a transcript, and hence from agene that is transcribed.

Expressible nucleic acid sequence: as used in the context of thisinvention is any nucleic acid sequence that is capable of beingtranscribed into RNA (e.g. mRNA, antisense RNA, double strand formingRNA etc.) or translated into a particular protein.

Expression: refers to the biosynthesis of a gene product. For example,in the case of a structural gene, expression involves transcription ofthe structural gene into mRNA and—optionally—the subsequent translationof mRNA into one or more polypeptides.

Functional equivalents: with regard to the inventive introns has to beunderstood as natural or artificial mutations of said introns describedin any of the SEQ ID NOs: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,15, 16, 17, 18, 19, 20, 21 or 22. Mutations can be insertions, deletionsor substitutions of one or more nucleic acids that do not diminish theexpression enhancing properties of said introns. These functionalequivalents having a identity of at least 80%, preferably 85%, morepreferably 90%, most preferably more than 95%, very especiallypreferably at least 98% identity—but less then 100% identity to theintron sequences as described by any of the SEQ ID NOs: 1, 2, 3, 5, 6,7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22, wherein saididentity is determined over a sequence of at least 95 consecutive basepairs, preferably at least 150 consecutive base pairs, more preferablyat least 200 consecutive base pairs of the sequence as described by anyof the SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21 or 22 and having essentially the same IME effectcharacteristics as the intron sequences as shown in any of the SEQ IDNOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or22.

Functional equivalents are in particular homologs of said intronsderived from other plant species. Homologs when used in reference tointrons refers to introns with expression enhancing properties isolatedfrom a genomic nucleic acid sequence that encodes for a protein

-   (i) sharing more than 60%, preferably 65%, 70%, 75%, 80%, more    preferably 85%, 90%, 95% or most preferably more than 95% sequence    identity on amino acid level with proteins that are encoded by genes    from which the inventive introns with the SEQ ID NOs: 1, 2, 3, 5, 6,    7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 have been    isolated, or-   (ii) catalyzing the same enzymatic reaction as the proteins encoded    by genes from which the inventive introns SEQ ID NOs: 1, 2, 3, 5, 6,    7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 have been    isolated, or-   (iii) showing comparable spatial and temporal expression pattern as    the proteins encoded by genes from which the inventive introns SEQ    ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19,    20, 21 or 22 have been isolated.

“Functional equivalents” as described above might have, compared withthe inventive introns a reduced or increased gene expression enhancingeffect. In this context, the gene expression enhancing effect of thefunctional equivalent intron is at least 50% higher, preferably at least100% higher, especially preferably at least 300% higher, very especiallypreferably at least 500% higher than a reference value obtained with anyof the introns shown in SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13,14, 15, 16, 17, 18, 19, 20, 21 or 22 under otherwise unchangedconditions.

Functionally linked or operably linked: is to be understood as meaning,for example, the sequential arrangement of a regulatory element (e.g. apromoter) with a nucleic acid sequence to be expressed and, ifappropriate, further regulatory elements (such as e.g., a terminator) insuch a way that each of the regulatory elements can fulfill its intendedfunction to allow, modify, facilitate or otherwise influence expressionof said nucleic acid sequence. The expression may result depending onthe arrangement of the nucleic acid sequences in relation to sense orantisense RNA. To this end, direct linkage in the chemical sense is notnecessarily required. Genetic control sequences such as, for example,enhancer sequences, can also exert their function on the target sequencefrom positions that are further away, or indeed from other DNAmolecules. The terms “functionally linked”, “operably linked,” “inoperable combination,” and “in operable order” as used herein withreference to an inventive intron with gene expression enhancingproperties refers to the linkage of at least one of said introns to anucleic acid sequences in a way that the expression enhancing effect isrealized and, if functional splice sites have been included, that theintron can be spliced out by the cell factors responsible for thesplicing procedure. In a preferred embodiment of the present invention,the intron is introduced into the 5′ non coding region of a nucleic acidsequence. Inventive expression constructs, wherein an inventive intronis functionally linked to an nucleic acid sequence are shown in theexamples. More preferred arrangements are those in which an intronfunctioning in intron mediated expression enhancement is insertedbetween a promoter and a nucleic acid sequence, preferably into thetranscribed nucleic acid sequence, or in case of a nucleic acid sequenceencoding for a protein, into the 5′ untranslated region of a nucleicacid sequence. The distance between the promoter sequence and thenucleic acid sequence to be expressed recombinantly is preferably lessthan 200 base pairs, especially preferably less than 100 base pairs,very especially preferably less than 50 base pairs. Operable linkage,and an expression cassette, can be generated by means of customaryrecombination and cloning techniques as are described, for example, inManiatis T, Fritsch E F and Sambrook J (1989) Molecular Cloning: ALaboratory Manual, Cold Spring Harbor Laboratory, Cold Spring Harbor(NY), in Silhavy T J, Berman M L and Enquist L W (1984) Experiments withGene Fusions, Cold Spring Harbor Laboratory, Cold Spring Harbor (NY), inAusubel F M et al. (1987) Current Protocols in Molecular Biology, GreenePublishing Assoc. and Wiley Interscience and in Gelvin et al. (1990) In:Plant Molecular Biology Manual. However, further sequences which, forexample, act as a linker with specific cleavage sites for restrictionenzymes, or as a signal peptide, may also be positioned between the twosequences. The insertion of sequences may also lead to the expression offusion proteins. Preferably, the expression construct, consisting of alinkage of promoter, intron and nucleic acid sequence to be expressed,can exist in a vector-integrated form and be inserted into a plantgenome, for example by transformation.

Gene: refers to a coding region operably linked to appropriateregulatory sequences capable of regulating the expression of thepolypeptide in some manner. A gene includes untranslated regulatoryregions of DNA (e.g., promoters, enhancers, repressors, etc.) preceding(upstream) and following (downstream) the coding region (open readingframe, ORF) as well as, where applicable, intervening sequences (i.e.,introns) between individual coding regions (i.e., exons). Genes may alsoinclude sequences located on both the 5′- and 3′-end of the sequences,which are present on the RNA transcript. These sequences are referred toas “flanking” sequences or regions (these flanking sequences are located5′ or 3′ to the non-translated sequences present on the mRNAtranscript). The 5′-flanking region may contain regulatory sequencessuch as promoters and enhancers, which control or influence thetranscription of the gene. The 3′-flanking region may contain sequences,which direct the termination of transcription, posttranscriptionalcleavage and polyadenylation.

Gene expression enhancing properties, gene expression enhancing effector intron mediated gene expression enhancement (IME): when made inreference to an intron sequence refers to the ability of the intron toenhance quantitatively the expression level of a nucleic acid sequence(e.g. a gene) that is part of an recombinant/transgenic DNA expressioncassette (as defined herein), measured on the basis of the transcribedRNA, mRNA, protein amount or protein activity compared to the otherwiseidentical expression construct lacking the intron under otherwiseunchanged conditions. Gene expression enhancing properties in plants:refers to an intron that is able to enhance quantitatively theexpression level of a plant derived nucleic acid sequence in a plant orplant cell and the enhancement of gene expression rate of a non-plantderived nucleic acid in a plant or a plant cell compared to theotherwise identical expression construct lacking the intron underotherwise unchanged conditions. In a preferred embodiment of theinvention, the expression enhancing effect is understood as an increasein the RNA steady state level, the protein steady state level or theprotein activity of a nucleic acid sequence or the corresponding protein(e.g. a reporter gene or protein) of at least 50%, or at least 100%, orat least 200%, 300%, 400% or at least 500%, 600%, 700%, 800%, 900% or atleast 1,000%, or more than 1,000% compared to the otherwise identicalexpression construct lacking the intron under otherwise unchangedconditions. Furthermore expression enhancing effect or intron mediatedenhancement has to be understood as the ability of an intron to changethe tissue, organ or cell specific expression pattern of a nucleic acidsequence (e.g. a gene) that is part of an inventive expression cassette.Changing the tissue, organ or cell specific expression pattern of anucleic acid sequence that is part of an inventive expression cassetterefers to the fact that due to the presence of an inventive intron, theexpression level (mRNA or encoded protein steady state level, or theactivity of a protein) of the respective gene is increased above thedetection threshold of the used detection method.

Gene silencing: can be realized by antisense or double-stranded RNA orby co-suppression (sense-suppression). The skilled worker knows that hecan use alternative cDNA or the corresponding gene as starting templatefor suitable antisense constructs. The “antisense” nucleic acid ispreferably complementary to the coding region of the target protein orpart thereof. However, the “antisense” nucleic acid may also becomplementary to the non-coding region or part thereof. Starting fromthe sequence information on a target protein, an antisense nucleic acidcan be designed in the manner with which the skilled worker is familiar,taking into consideration Watson's and Crick's rules of base pairing. Anantisense nucleic acid can be complementary to the entire or part of thenucleic acid sequence of a target protein.

Likewise encompassed is the use of the above-described sequences insense orientation, which, as is known to the skilled worker, can lead toco-suppression (sense-suppression). It has been demonstrated thatexpression of sense nucleic acid sequences can reduce or switch offexpression of the corresponding gene, analogously to what has beendescribed for antisense approaches (Goring (1991) Proc. Natl. Acad. Sci.USA 88:1770-1774; Smith (1990) Mol. Gen. Genet. 224:447-481; Napoli(1990) Plant Cell 2:279-289; Van der Krol (1990) Plant Cell 2:291-299).In this context, the construct introduced may represent the gene to bereduced fully or only in part. The possibility of translation is notnecessary. Especially preferred is the use of gene regulation methods bymeans of double-stranded RNAi (“double-stranded RNA interference”). Suchmethods are known to the person skilled in the art (e.g., Matzke 2000;Fire 1998; WO 99/32619; WO 99/53050; WO 00/68374; WO 00/44914; WO00/44895; WO 00/49035; WO 00/63364). The processes and methods describedin the references stated are expressly referred to.

Genome and genomic DNA of an organism as used herein is the wholehereditary information of an organism that is encoded in the DNA (or,for some viruses, RNA). This includes both the genes and the non-codingsequences. Said genomic DNA comprises the DNA of the nucleus (alsoreferred to as chromosomal DNA) but also the DNA of the plastids (e.g.,chloroplasts) and other cellular organelles (e.g., mitochondria).Preferably the terms genome or genomic DNA is referring to thechromosomal DNA of the nucleus. The term “chromosomal DNA” or“chromosomal DNA-sequence” is to be understood as the genomic DNA of thecellular nucleus independent from the cell cycle status. Chromosomal DNAmight therefore be organized in chromosomes or chromatids, they might becondensed or uncoiled. An insertion into the chromosomal DNA can bedemonstrated and analyzed by various methods known in the art like e.g.,polymerase chain reaction (PCR) analysis, Southern blot analysis,fluorescence in situ hybridization (FISH), and in situ PCR.

Heterologous: with respect to a nucleic acid sequence refers to anucleotide sequence, which is ligated to a nucleic acid sequence towhich it is not ligated in nature, or to which it is ligated at adifferent location in nature.

Hybridizing: as used herein includes “any process by which a strand ofnucleic acid joins with a complementary strand through base pairing.”(Coombs 1994, Dictionary of Biotechnology, Stockton Press, New YorkN.Y.). Hybridization and the strength of hybridization (i.e., thestrength of the association between the nucleic acids) is impacted bysuch factors as the degree of complementarity between the nucleic acids,stringency of the conditions involved, the Tm of the formed hybrid, andthe G:C ratio within the nucleic acids. As used herein, the term “Tm” isused in reference to the “melting temperature.” The melting temperatureis the temperature at which a population of double-stranded nucleic acidmolecules becomes half dissociated into single strands. The equation forcalculating the Tm of nucleic acids is well known in the art. Asindicated by standard references, a simple estimate of the Tm value maybe calculated by the equation: Tm=81.5+0.41 (% G+C), when a nucleic acidis in aqueous solution at 1 M NaCl [see e.g., Anderson and Young,Quantitative Filter Hybridization, in Nucleic Acid Hybridization(1985)]. Other references include more sophisticated computations, whichtake structural as well as sequence characteristics into account for thecalculation of Tm. The person skilled in the art knows well thatnumerous hybridization conditions may be employed to comprise either lowor high stringency conditions; factors such as the length and nature(DNA, RNA, base composition) of the probe and nature of the target (DNA,RNA, base composition, present in solution or immobilized, etc.) and theconcentration of the salts and other components (e.g., the presence orabsence of form amide, dextran sulfate, polyethylene glycol) areconsidered and the hybridization solution may be varied to generateconditions of either low or high hybridization stringency Those skilledin the art know that higher stringencies are preferred to reduce oreliminate non-specific binding between the nucleotide sequence of aninventive intron and other nucleic acid sequences, whereas lowerstringencies are preferred to detect a larger number of nucleic acidsequences having different homologies to the inventive nucleotidesequences. Such conditions are described by, e.g., Sambrook (MolecularCloning; A Laboratory Manual, 2nd Edition, Cold Spring Harbor LaboratoryPress, Cold Spring Harbor, N.Y. (1989)) or in Current Protocols inMolecular Biology, John Wiley & Sons, N.Y. (1989) 6.3.1-6.3.6. Preferredhybridization condition are disclose in the detailed description.

Identity: when used in relation to nucleic acids refers to a degree ofcomplementarity. Identity between two nucleic acids is understood asmeaning the identity of the nucleic acid sequence over in each case theentire length of the sequence, which is calculated by comparison withthe aid of the program algorithm GAP (Wisconsin Package Version 10.0,University of Wisconsin, Genetics Computer Group (GCG), Madison, USA)with the parameters being set as follows:

-   -   Gap Weight: 12 Length Weight: 4    -   Average Match: 2,912 Average Mismatch:−2,003

For example, a sequence with at least 95% identity to the sequence SEQID NO. 1 at the nucleic acid level is understood as meaning the sequencethat, upon comparison with the sequence SEQ ID NO. 1 by the aboveprogram algorithm with the above parameter set, has at least 95%identity. There may be partial identity (i.e., partial identity of lessthen 100%) or complete identity (i.e., complete identity of 100%).

Introducing a recombinant DNA expression construct: in plant cellsrefers to a recombinant DNA expression construct that will be introducedinto the genome of a plant by transformation and is stably maintained.The term “introducing” encompasses for example methods such astransfection, transduction or transformation.

Identification, “Identifying” or “selecting”: with regard totransformation of plants has to be understood as a screening procedureto identify and select those plant cells in which the recombinantexpression construct has been introduced stably into the genome.“Identifying” with regard to an intron with gene expression enhancingproperties refers to a process for the selection of said intron out of apopulation of introns. Preferably, “identifying” refers to an in silicoselection process, more preferably to an automated in silico selectionprocess, using the selection criteria of the inventive methods. Such anin silico identification process can comprise for instance the steps of

-   (1) generating an intron sequence database on the basis of DNA    sequences present in a DNA sequence database (e.g. genomic DNA    databases publicly available via the internet),-   (2) screening of the generated intron DNA sequence database—or other    genomic DNA sequences containing databases—for introns with gene    expression enhancing properties using the criteria according to the    inventive method,

wherein the steps for retrieving or generating the DNA sequences, thegeneration of an intron specific DNA sequence database and the screeningof these DNA sequences—using the criteria according to the inventivemethod—will be performed with the aid of appropriate computer algorithmsand computer devices.

Intron: refers to sections of DNA (intervening sequences) within a genethat do not encode part of the protein that the gene produces, and thatis spliced out of the mRNA that is transcribed from the gene before itis exported from the cell nucleus. Intron sequence refers to the nucleicacid sequence of an intron. Thus, introns are those regions of DNAsequences that are transcribed along with the coding sequence (exons)but are removed during the formation of mature mRNA. Introns can bepositioned within the actual coding region or in either the 5′ or 3′untranslated leaders of the pre-mRNA (unspliced mRNA). Introns in theprimary transcript are excised and the coding sequences aresimultaneously and precisely ligated to form the mature mRNA. Thejunctions of introns and exons form the splice site. The sequence of anintron begins with GU and ends with AG. Furthermore, in plants, twoexamples of AU-AC introns have been described: the fourteenth intron ofthe RecA-like protein gene and the seventh intron of the G5 gene fromArabidopsis thaliana are AT-AC introns. Pre-mRNAs containing intronshave three short sequences that are—beside other sequences—essential forthe intron to be accurately spliced. These sequences are the 5′splice-site, the 3′ splice-site, and the branchpoint. mRNA splicing isthe removal of intervening sequences (introns) present in primary mRNAtranscripts and joining or ligation of exon sequences. This is alsoknown as cis-splicing which joins two exons on the same RNA with theremoval of the intervening sequence (intron). The functional elements ofan intron comprising sequences that are recognized and bound by thespecific protein components of the spliceosome (e.g. splicing consensussequences at the ends of introns). The interaction of the functionalelements with the spliceosome results in the removal of the intronsequence from the premature mRNA and the rejoining of the exonsequences. Introns have three short sequences that areessential—although not sufficient—for the intron to be accuratelyspliced. These sequences are the 5′ splice site, the 3′ splice site andthe branch point. The branchpoint sequence is important in splicing andsplice-site selection in plants. The branchpoint sequence is usuallylocated 10-60 nucleotides upstream of the 3′ splice site. Plantsequences exhibit sequence deviations in the branchpoint, the consensussequences being 5-CURAY-3′ (SEQ ID NO:75) or 5′-YURAY-3′ (SEQ ID NO:76).

“IME-intron” or intron mediated enhancement (IME)-intron: when made inreference to an intron sequence refers to an intron with gene expressionenhancing properties in plants as defined herein (see gene expressionenhancing properties, gene expression enhancing effect or intronmediated gene expression enhancement).

Isolation or isolated: when used in relation to an intron or gene, as in“isolation of an intron sequence” or “isolation of a gene” refers to anucleic acid sequence that is identified within and isolated/separatedfrom its chromosomal nucleic acid sequence context within the respectivesource organism. Isolated nucleic acid is nucleic acid present in a formor setting that is different from that in which it is found in nature.In contrast, non-isolated nucleic acids are nucleic acids such as DNAand RNA, which are found in the state they exist in nature. For example,a given DNA sequence (e.g. a gene) is found on the host cell chromosomein proximity to neighboring genes; intron sequences, are imbedded intothe nucleic acid sequence of a gene in an alternating sequence ofintrons and exons. The isolated nucleic acid sequence may be present insingle-stranded or double-stranded form. When an isolated nucleic acidsequence is to be utilized to express a protein, the nucleic acidsequence will contain at a minimum at least a portion of the sense orcoding strand (i.e., the nucleic acid sequence may be single-stranded).Alternatively, it may contain both the sense and anti-sense strands(i.e., the nucleic acid sequence may be double-stranded).

Nucleic acid: refers to deoxyribonucleotides, ribonucleotides orpolymers or hybrids thereof in single- or double-stranded, sense orantisense form. Unless otherwise indicated, a particular nucleic acidsequence also implicitly encompasses conservatively modified variantsthereof (e.g., degenerate codon substitutions) and complementarysequences, as well as the sequence explicitly indicated. The term“nucleic acid” can be used to describe a “gene”, “cDNA”,“DNA” “mRNA”,“oligonucleotide,” and “polynucleotide”.

Nucleic acid sequence: as used herein refers to the consecutive sequenceof deoxyribonucleotides or ribonucleotides (nucleotides) of a DNAfragment (oligonucleotide, polynucleotide, genomic DNA, cDNA etc.) as itcan made be available by DNA sequencing techniques as a list ofabbreviations, letters, characters or words, which representnucleotides.

Organ: with respect to a plant (or “plant organ”) means parts of a plantand may include (but shall not limited to) for example roots, fruits,shoots, stem, leaves, anthers, sepals, petals, pollen, seeds, etc.

Otherwise unchanged conditions: means—for example—that the expressionwhich is initiated by one of the expression constructs to be compared isnot modified by combination with additional genetic control sequences,for example enhancer sequences and is done in the same environment(e.g., the same plant species) at the same developmental stage and underthe same growing conditions.

Plant: is generally understood as meaning any single- or multi-celledorganism or a cell, tissue, organ, part or propagation material (such asseeds or fruit) of same which is capable of photosynthesis. Included forthe purpose of the invention are all genera and species of higher andlower plants of the Plant Kingdom. Annual, perennial, monocotyledonousand dicotyledonous plants are preferred. The term includes the matureplants, seed, shoots and seedlings and their derived parts, propagationmaterial (such as seeds or microspores), plant organs, tissue,protoplasts, callus and other cultures, for example cell cultures, andany other type of plant cell grouping to give functional or structuralunits. Mature plants refer to plants at any desired developmental stagebeyond that of the seedling. Seedling refers to a young immature plantat an early developmental stage. Annual, biennial, monocotyledonous anddicotyledonous plants are preferred host organisms for the generation oftransgenic plants. The expression of genes is furthermore advantageousin all ornamental plants, useful or ornamental trees, flowers, cutflowers, shrubs or lawns. Plants which may be mentioned by way ofexample but not by limitation are angiosperms, bryophytes such as, forexample, Hepaticae (liverworts) and Musci (mosses); Pteridophytes suchas ferns, horsetail and club mosses; gymnosperms such as conifers,cycads, ginkgo and Gnetatae; algae such as Chlorophyceae, Phaeophpyceae,Rhodophyceae, Myxophyceae, Xanthophyceae, Bacillariophyceae (diatoms),and Euglenophyceae. Preferred are plants which are used for food or feedpurpose such as the families of the Leguminosae such as pea, alfalfa andsoya; Gramineae such as rice, maize, wheat, barley, sorghum, millet,rye, triticale, or oats; the family of the Umbelliferae, especially thegenus Daucus, very especially the species carota (carrot) and Apium,very especially the species Graveolens dulce (celery) and many others;the family of the Solanaceae, especially the genus Lycopersicon, veryespecially the species esculentum (tomato) and the genus Solanum, veryespecially the species tuberosum (potato) and melongena (egg plant), andmany others (such as tobacco); and the genus Capsicum, very especiallythe species annuum (peppers) and many others; the family of theLeguminosae, especially the genus Glycine, very especially the speciesmax (soybean), alfalfa, pea, lucerne, beans or peanut and many others;and the family of the Cruciferae (Brassicacae), especially the genusBrassica, very especially the species napus (oil seed rape), campestris(beet), oleracea cv Tastie (cabbage), oleracea cv Snowball Y(cauliflower) and oleracea cv Emperor (broccoli); and of the genusArabidopsis, very especially the species thaliana and many others; thefamily of the Compositae, especially the genus Lactuca, very especiallythe species sativa (lettuce) and many others; the family of theAsteraceae such as sunflower, Tagetes, lettuce or Calendula and manyother; the family of the Cucurbitaceae such as melon, pumpkin/squash orzucchini, and linseed. Further preferred are cotton, sugar cane, hemp,flax, chillies, and the various tree, nut and wine species.

Providing: when used in relation to an intron as in “physicallyproviding an intron” refers to the cloning of the DNA sequencerepresenting said intron from a plant of interest and the provision ofsuch an intron physically in an appropriate vector or plasmid forfurther cloning work and the subsequent application of said intronaccording to the invention.

Producing: when used in relation to an intron as in “producing anintron” refers to the synthesis of DNA molecules on the basis of DNAsequence information of an inventive intron.

Promoter, promoter element, or promoter sequence: as used herein, refersto a DNA sequence which when ligated to a nucleotide sequence ofinterest is capable of controlling the transcription of the nucleotidesequence of interest into mRNA. Thus, a promoter is a recognition siteon a DNA sequence that provide an expression control element for a geneand to which RNA polymerase specifically binds and initiates RNAsynthesis (transcription) of that gene. A promoter is typically, thoughnot necessarily, located 5′ (i.e., upstream) of a nucleotide sequence ofinterest (e.g., proximal to the transcriptional start site of astructural gene). Promoters may be tissue specific or cell specific. Theterm “tissue specific” as it applies to a promoter refers to a promoterthat is capable of directing selective expression of a nucleotidesequence of interest to a specific type of tissue (e.g., petals) in therelative absence of expression of the same nucleotide sequence ofinterest in a different type of tissue (e.g., roots). Promoters may beconstitutive or regulatable. The term “constitutive” when made inreference to a promoter means that the promoter is capable of directingtranscription of an operably linked nucleic acid sequence in the absenceof a stimulus (e.g., heat shock, chemicals, light, etc.). Typically,constitutive promoters are capable of directing expression of atransgene in substantially any cell and any tissue. In contrast, a“regulatable” promoter is one which is capable of directing a level oftranscription of an operably linked nuclei acid sequence in the presenceof a stimulus (e.g., heat shock, chemicals, light, etc.) which isdifferent from the level of transcription of the operably linked nucleicacid sequence in the absence of the stimulus. A promoter sequencefunctioning in plants is understood as meaning, in principle, anypromoter which is capable of governing the expression of genes, inparticular foreign genes, in plants or plant parts, plant cells, planttissues or plant cultures. In this context, expression can be, forexample, constitutive, inducible or development-dependent. Aconstitutive promoter is a promoter where the rate of RNA polymerasebinding and initiation is approximately constant and relativelyindependent of external stimuli. Usable promoters are constitutivepromoters (Benfey et al. (1989) EMBO J. 8:2195-2202), such as thosewhich originate from plant viruses, such as 35S CAMV (Franck et al.(1980) Cell 21:285-294), 19S CaMV (see also U.S. Pat. No. 5,352,605 andWO 84/02913), 34S FMV (Sanger et al. (1990) Plant. Mol. Biol.,14:433-443), the parsley ubiquitin promoter, or plant promoters such asthe Rubisco small subunit promoter described in U.S. Pat. No. 4,962,028or the plant promoters PRP1 [Ward et al. (1993) Plant. Mol. Biol. 22:361-6], SSU, PGEL1, OCS [Leisner (1988) Proc Natl Acad Sci USA85(5):2553-2557], lib4, usp, mas [Comai (1990) Plant Mol Biol15(3):373-381], STLS1, ScBV (Schenk (1999) Plant Mol Biol39(6):1221-1230), B33, SAD1 or SAD2 (flax promoters, Jain et al. (1999)Crop Science 39(6):1696-1701) or nos [Shaw et al. (1984) Nucleic AcidsRes. 12(20):7831-7846]. An inducible promoter is a promoter where therate of RNA polymerase binding and initiation is modulated by externalstimuli. Such stimuli include light, heat, anaerobic stress, alterationin nutrient conditions, presence or absence of a metabolite, presence ofa ligand, microbial attack, wounding and the like (for a review, seeGatz (1997) Annu. Rev. Plant Physiol. Plant Mol. Biol. 48:89-108).Chemically inducible promoters are particularly suitable when it isdesired to express the gene in a time-specific manner. Examples of suchpromoters are a salicylic acid inducible promoter (WO 95/19443), andabscisic acid-inducible promoter (EP 335 528), a tetracycline-induciblepromoter (Gatz et al. (1992) Plant J. 2:397-404), a cyclohexanol- orethanol-inducible promoter (WO 93/21334) or others as described herein.A viral promoter is a promoter with a DNA sequence substantially similarto the promoter found at the 5′ end of a viral gene. A typical viralpromoter is found at the 5′ end of the gene coding for the p21 proteinof MMTV described by Huang et al. ((1981) Cell 27:245). A syntheticpromoter is a promoter that was chemically synthesized rather thanbiologically derived. Usually synthetic promoters incorporate sequencechanges that optimize the efficiency of RNA polymerase initiation. Atemporally regulated promoter is a promoter where the rate of RNApolymerase binding and initiation is modulated at a specific time duringdevelopment. Examples of temporally regulated promoters are given inChua et al. [(1989) Science 244:174-181]. A spatially regulated promoteris a promoter where the rate of RNA polymerase binding and initiation ismodulated in a specific structure of the organism such as the leaf, stemor root. Examples of spatially regulated promoters are given in Chua etal. [(1989) Science 244:174-181]. A spatiotemporally regulated promoteris a promoter where the rate of RNA polymerase binding and initiation ismodulated in a specific structure of the organism at a specific timeduring development. A typical spatiotemporally regulated promoter is theEPSP synthase-35S promoter described by Chua et al. [(1989) Science244:174-181]. Suitable promoters are furthermore the oilseed rape napingene promoter (U.S. Pat. No. 5,608,152), the Vicia faba USP promoter(Bäumlein et al. (1991) Mol Gen Genet. 225(3):459-67), the Arabidopsisoleosin promoter (WO 98/45461), the Phaseolus vulgaris phaseolinpromoter (U.S. Pat. No. 5,504,200), the Brassica Bce4 promoter (WO91/13980), the bean arc5 promoter, the carrot DcG3 promoter, or theLegumin B4 promoter (LeB4; Bäumlein et al. (1992) Plant Journal2(2):233-9), and promoters which bring about the seed-specificexpression in monocotyledonous plants such as maize, barley, wheat, rye,rice and the like. Advantageous seed-specific promoters are the sucrosebinding protein promoter (WO 00/26388), the phaseolin promoter and thenapin promoter. Suitable promoters which must be considered are thebarley Ipt2 or Ipt1 gene promoter (WO 95/15389 and WO 95/23230), and thepromoters described in WO 99/16890 (promoters from the barley hordeingene, the rice glutelin gene, the rice oryzin gene, the rice prolamingene, the wheat gliadin gene, the wheat glutelin gene, the maize zeingene, the oat glutelin gene, the sorghum kasirin gene and the ryesecalin gene). Further suitable promoters are Amy32b, Amy 6-6 andAleurain [U.S. Pat. No. 5,677,474], Bce4 (oilseed rape) [U.S. Pat. No.5,530,149], glycinin (soya) [EP 571 741], phosphoenolpyruvatecarboxylase (soya) [JP 06/62870], ADR12-2 (soya) [WO 98/08962],isocitrate lyase (oilseed rape) [U.S. Pat. No. 5,689,040] or α-amylase(barley) [EP 781 849]. Other promoters which are available for theexpression of genes in plants are leaf-specific promoters such as thosedescribed in DE-A 19644478 or light-regulated promoters such as, forexample, the pea petE promoter. Further suitable plant promoters are thecytosolic FBPase promoter or the potato ST-LSI promoter (Stockhaus etal. (1989) EMBO J. 8:2445), the Glycine max phosphoribosylpyrophosphateamidotransferase promoter (GenBank Accession No. U87999) or thenode-specific promoter described in EP-A-0 249 676. Other suitablepromoters are those which react to biotic or abiotic stress conditions,for example the pathogen-induced PRP1 gene promoter (Ward et al. (1993)Plant. Mol. Biol. 22:361-366), the tomato heat-inducible hsp80 promoter(U.S. Pat. No. 5,187,267), the potato chill-inducible alpha-amylasepromoter (WO 96/12814) or the wound-inducible pinII promoter (EP-A-0 375091) or others as described herein. Other promoters, which areparticularly suitable, are those that bring about plastid-specificexpression. Suitable promoters such as the viral RNA polymerase promoterare described in WO 95/16783 and WO 97/06250, and the Arabidopsis clpPpromoter, which is described in WO 99/46394. Other promoters, which areused for the strong expression of heterologous sequences in as manytissues as possible, in particular also in leaves, are, in addition toseveral of the abovementioned viral and bacterial promoters, preferably,plant promoters of actin or ubiquitin genes such as, for example, therice actin1 promoter. Further examples of constitutive plant promotersare the sugarbeet V-ATPase promoters (WO 01/14572). Examples ofsynthetic constitutive promoters are the Super promoter (WO 95/14098)and promoters derived from G-boxes (WO 94/12015). If appropriate,chemical inducible promoters may furthermore also be used, compare EP-A388186, EP-A 335528, WO 97/06268. The above listed promoters can becomprise other regulatory elements that affect gene expression inresponse to plant hormones (Xu et al., 1994, Plant Cell 6(8):1077-1085)biotic or abiotic environmental stimuli, such as stress conditions, asexemplified by drought (Tran et al. (2004) Plant Cell 16(9):2481-2498),heat, chilling, freezing, salt stress, oxidative stress (U.S. Pat. No.5,290,924) or biotic stressors like bacteria, fungi or viruses.

Polypeptide, peptide, oligopeptide, gene product, expression product andprotein: are used interchangeably herein to refer to a polymer oroligomer of consecutive amino acid residues.

Recombinant or transgenic DNA expression construct: with respect to, forexample, a nucleic acid sequence (expression construct, expressioncassette or vector comprising said nucleic acid sequence) refers to allthose constructs originating by experimental manipulations in whicheither

-   a) said nucleic acid sequence, or-   b) a genetic control sequence linked operably to said nucleic acid    sequence (a), for example a promoter, or-   c) (a) and (b)    is not located in its natural genetic environment or has been    modified by experimental manipulations, an example of a modification    being a substitution, addition, deletion, inversion or insertion of    one or more nucleotide residues. Natural genetic environment refers    to the natural chromosomal locus in the organism of origin, or to    the presence in a genomic library. In the case of a genomic library,    the natural genetic environment of the nucleic acid sequence is    preferably retained, at least in part. The environment flanks the    nucleic acid sequence at least at one side and has a sequence of at    least 50 bp, preferably at least 500 bp, especially preferably at    least 1,000 bp, very especially preferably at least 5,000 bp, in    length. A naturally occurring expression construct—for example the    naturally occurring combination of a promoter with the corresponding    gene—becomes a transgenic expression construct when it is modified    by non-natural, synthetic “artificial” methods such as, for example,    mutagenesis. Such methods have been described (U.S. Pat. No.    5,565,350; WO 00/15815). Recombinant polypeptides or proteins: refer    to polypeptides or proteins produced by recombinant DNA techniques,    i.e., produced from cells transformed by an exogenous recombinant    DNA construct encoding the desired polypeptide or protein.    Recombinant nucleic acids and polypeptide may also comprise    molecules which as such does not exist in nature but are modified,    changed, mutated or otherwise manipulated by man. An important use    of the intron sequences of the invention will be the enhancement of    the expression of a nucleic acid sequence, which encodes a    particular protein, a polypeptide or DNA sequences that interfere    with normal transcription or translation, e.g. interference- or    antisense-RNA. In one embodiment of the present invention, the    recombinant DNA expression construct confers expression of one or    more nucleic acid molecules. Said recombinant DNA expression    construct according to the invention advantageously encompasses a    promoter functioning in plants, additional regulatory or control    elements or sequences functioning in plants, an intron sequence with    expression enhancing properties in plants and a terminator    functioning in plants. Additionally, the recombinant expression    construct might contain additional functional elements such as    expression cassettes conferring expression of e.g. positive and    negative selection markers, reporter genes, recombinases or    endonucleases effecting the production, amplification or function of    the expression cassettes, vectors or recombinant organisms according    to the invention. Furthermore, the recombinant expression construct    can comprise nucleic acid sequences homologous to a plant gene of    interest having a sufficient length in order to induce a homologous    recombination (HR) event at the locus of the gene of interest after    introduction in the plant. A recombinant transgenic expression    cassette of the invention (or a transgenic vector comprising said    transgenic expression cassette) can be produced by means of    customary recombination and cloning techniques as are described (for    example, in Maniatis 1989, Molecular Cloning: A Laboratory Manual,    2nd Ed., Cold Spring Harbor Laboratory, Cold Spring Harbor (NY);    Silhavy 1984,) Experiments with Gene Fusions, Cold Spring Harbor    Laboratory, Cold Spring Harbor, N.Y.; and in Ausubel 1987, Current    Protocols in Molecular Biology, Greene Publishing Assoc. and Wiley    Interscience). The introduction of an expression cassette according    to the invention into an organism or cells, tissues, organs, parts    or seeds thereof (preferably into plants or plant cells, tissue,    organs, parts or seeds) can be effected advantageously using    vectors, which comprise the above described nucleic acids,    promoters, introns, terminators, regulatory or control elements and    functional elements.

Regeneration: as used herein, means growing a whole plant from a plantcell, a group of plant cells, a plant part or a plant piece (e.g., froma protoplast, callus, protocorm-like body, or tissue part).

Regulatory sequence: refers to promoters, enhancer or other segments ofDNA where regulatory proteins such as transcription factors bind andthereby influencing the transcription rate of a given gene.

Substantially all introns of a plant genome represented in a genomic DNAsequence database or genomic DNA library: refers to more than 80%,preferably to more than 90%, more preferably to more than 95%, stillmore preferably more than 98% of all introns present in the genome ofthe plant used as a source for the preparation of the genomic DNAsequence database or genomic DNA library. The construction of genomiclibraries and the subsequent sequencing of the genomic DNA and theconstruction of a genomic or genome DNA sequence database using theobtained sequence information is well established in the art (Mozo etal. (1998) Mol. Gen. Genet. 258:562-570; Choi et al. (1995) Weeds World2:17-20; Lui et al. (1999) Proc. Natl. Acad. Sci. USA 96:6535-6540; TheArabidopsis Genome initiative, Nature 402:761-777 (1999); TheArabidopsis Genome initiative, Nature 408:796-826 (2000).

Structural gene: as used herein is intended to mean a DNA sequence thatis transcribed into mRNA which is then translated into a sequence ofamino acids characteristic of a specific polypeptide.

Sufficient length: with respect to a homology sequence comprised in aDNA-construct (e.g., the homology sequence A or B) is to be understoodto comprise sequences of a length of at least 100 base pair, preferablyat least 250 base pair, more preferably at least 500 base pair,especially preferably at least 1,000 base pair, most preferably at least2,500 base pair. The term “sufficient homology” with respect to ahomology sequence comprised in a DNA-construct (e.g., the homologysequence A or B) is to be understood to comprise sequences having ahomology to the corresponding target sequence comprised in thechromosomal DNA (e.g., the target sequence A′ or B′) of at least 70%,preferably at least 80%, more preferably at least 90%, especiallypreferably at least 95%, more especially preferably at least 99%, mostpreferably 100%, wherein said homology extends over a length of at least50 base pair, preferably at least 100 base pair, more preferably atleast 250 base pair, most preferably at least 500 base pair.

Target region/sequence: of a nucleic acid sequence is a portion of anucleic acid sequence that is identified to be of interest. A “codingregion” of a nucleic acid sequence is the portion of the nucleic acidsequence, which is transcribed and translated in a sequence-specificmanner to produce into a particular polypeptide or protein when placedunder the control of appropriate regulatory sequences. The coding regionis said to encode such a polypeptide or protein.

Tissue: with respect to a plant (or “plant tissue”) means arrangement ofmultiple plant cells including differentiated and undifferentiatedtissues of plants. Plant tissues may constitute part of a plant organ(e.g., the epidermis of a plant leaf) but may also constitute tumortissues and various types of cells in culture (e.g., single cells,protoplasts, embryos, calli, protocorm-like bodies, etc.). Plant tissuemay be in planta, in organ culture, tissue culture, or cell culture.

Transforming or transformation: as used herein refers to theintroduction of genetic material (e.g., a transgene) into a cell.Transformation of a cell may be stable or transient. The term “transienttransformation” or “transiently transformed” refers to the introductionof one or more transgenes into a cell in the absence of integration ofthe transgene into the host cell's genome. Transient transformation maybe detected by, for example, enzyme-linked immunosorbent assay (ELISA)which detects the presence of a polypeptide encoded by one or more ofthe transgenes. Alternatively, transient transformation may be detectedby detecting the activity of the protein (e.g., β-glucuronidase) encodedby the transgene (e.g., the uidA gene) as demonstrated herein [e.g.,examples 1.6 and 2.4, histochemical assay of GUS enzyme activity bystaining with X-gluc which gives a blue precipitate in the presence ofthe GUS enzyme; and a chemiluminescent assay of GUS enzyme activityusing the GUS-Light kit (Tropix)]. The term “transient transformant”refers to a cell which has transiently incorporated one or moretransgenes. In contrast, the term “stable transformation” or “stablytransformed” refers to the introduction and integration of one or moretransgenes into the genome of a cell, preferably resulting inchromosomal integration and stable heritability through meiosis. Stabletransformation of a cell may be detected by Southern blot hybridizationof genomic DNA of the cell with nucleic acid sequences, which arecapable of binding to one or more of the transgenes. Alternatively,stable transformation of a cell may also be detected by the polymerasechain reaction of genomic DNA of the cell to amplify transgenesequences. The term “stable transformant” refers to a cell that hasstably integrated one or more transgenes into the genomic DNA. Thus, astable transformant is distinguished from a transient transformant inthat, whereas genomic DNA from the stable transformant contains one ormore transgenes, genomic DNA from the transient transformant does notcontain a transgene. Transformation also includes introduction ofgenetic material into plant cells in the form of plant viral vectorsinvolving extrachromosomal replication and gene expression, which mayexhibit variable properties with respect to meiotic stability.

Transgenic or recombinant: when used in reference to a cell refers to acell which contains a transgene, or whose genome has been altered by theintroduction of a transgene. The term “transgenic” when used inreference to a tissue or to a plant refers to a tissue or plant,respectively, which comprises one or more cells that contain atransgene, or whose genome has been altered by the introduction of atransgene. Transgenic cells, tissues and plants may be produced byseveral methods including the introduction of a “transgene” comprisingnucleic acid (usually DNA) into a target cell or integration of thetransgene into a chromosome of a target cell by way of humanintervention, such as by the methods described herein.

Wild-type, natural or of natural origin: means with respect to anorganism, polypeptide, or nucleic acid sequence, that said organismpolypeptide, or nucleic acid sequence is naturally occurring oravailable in at least one naturally occurring organism polypeptide, ornucleic acid sequence which is not changed, mutated, or otherwisemanipulated by man.

Vector: is a DNA molecule capable of replication in a host cell.Plasmids and cosmids are exemplary vectors. Furthermore, the terms“vector” and “vehicle” are used interchangeably in reference to nucleicacid molecules that transfer DNA segment(s) from one cell to another,whereby the cells not necessarily belonging to the same organism (e.g.transfer of a DNA segment form an Agrobacterium cell to a plant cell).

The term “expression vector” as used herein refers to a recombinant DNAmolecule containing a desired coding sequence and appropriate nucleicacid sequences necessary for the expression of the operably linkedcoding sequence in a particular host organism.

DETAILED DESCRIPTION OF THE INVENTION

The teaching of the present invention enables the identification ofintrons causing intron mediated enhancement (IME) of gene expression.Furthermore, the present invention provides isolated plant introns that,if functionally combined with a promoter functioning in plants and anucleic acid fragment, can enhance the expression rate of said nucleicacid in a plant or a plant cell.

A first embodiment of the present invention relates to a method foridentifying an intron with plant gene expression enhancing propertiescomprising selecting an intron from a plant genome, wherein said intronis characterized by at least the following features

-   I) an intron length shorter than 1,000 base pairs, and-   II) presence of a 5′ splice site comprising the dinucleotide    sequence 5′-GT-3′ (SEQ ID NO: 78), and-   III) presence of a 3′ splice site comprising the trinucleotide    sequence 5′-CAG-3′ (SEQ ID NO: 79), and-   IV) presence of a branch point resembling the consensus sequence    5′-CURAY-3′ (SEQ ID NO:75) upstream of the 3′ splice site, and-   V) an adenine plus thymine content of at least 40% over 100    nucleotides downstream from the 5′ splice site, and-   VI) an adenine plus thymine content of at least 50% over 100    nucleotides upstream from the 3′ splice site, and-   VII) an adenine plus thymine content of at least 50%, and a thymine    content of at least 30% over the entire intron.

In another embodiment, the invention relates to a method for enrichingthe number of introns with expression enhancing properties in plants ina population of plant introns to a percentage of at least 50% of saidpopulation, said method comprising selecting introns from saidpopulation, said introns are characterized by at least the followingfeatures

-   I) an intron length shorter than 1,000 base pairs, and-   II) presence of a 5′ splice site comprising the dinucleotide    sequence 5′-GT-3′ (SEQ ID NO: 78), and-   III) presence of a 3′ splice site comprising the trinucleotide    sequence 5′-CAG-3′ (SEQ ID NO: 79), and-   IV) presence of a branch point resembling the consensus sequence    5′-CURAY-3′ (SEQ ID NO:75) upstream of the 3′ splice site, and-   V) an adenine plus thymine content of at least 40% over 100    nucleotides downstream from the 5′ splice site, and-   VI) an adenine plus thymine content of at least 50% over 100    nucleotides upstream from the 3′ splice site, and-   VII) an adenine plus thymine content of at least 50%, and a thymine    content of at least 30% over the entire intron.

The inclusion of any of the inventive introns described by SEQ ID NOs:1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22into the 5′ untranslated region (UTR) of the β-glucuronidase gene (GUS)driven by the Zea mays Ubiquitin promoter has led to strong expressionenhancement of the reporter gene in maize protoplasts (Black MexicanSweet) suspension cells and stable transformed plants (see examples).Furthermore, it could be shown that the gene expression enhancementproperties of said introns are comparable to those known from theliterature (e.g. the first intron of the Zea mays Ubiquitin gene, usedas positive control in the expression assays).

In a preferred embodiment, the number of introns—with gene expressionenhancing properties—identified within a population of introns byapplying the method of the invention for enrichment is enriched to apercentage of at least 50%, preferably at least 55%, more preferably atleast 60%, especially preferably at least 65%, or very especiallypreferably at least 70% (i.e., a given population of 100 intronspre-selected by using the inventive method will comprise at least 50,preferably at least 55, more preferably at least 60, especiallypreferably at least 65 or 70 introns with gene expression enhancingproperties). More preferably, the number of introns—with gene expressionenhancing properties—identified within a population of introns byapplying the method of the invention for enrichment is enriched to apercentage of at least 50%, wherein the selected introns, if part of anrecombinant DNA expression construct leads to an increase in the geneexpression of a given gene of at least 300% compared to the otherwiseidentical expression construct lacking the intron under otherwiseunchanged conditions. Most preferably, the enrichment is at least 60%percent, wherein the selected introns, increasing the transcription of agene driven by a given promoter of at least 200%. Especially preferably,the enrichment is at least 70%, wherein the selected introns, increasingthe transcription of a gene driven by a given promoter of at least 50%.

Preferably, the length of an inventive IME-intron is preferably shorterthan 1,000 base pairs, more preferably shorter than 900 bp, mostpreferably shorter than 800 bp. In a preferred embodiment, thebranchpoint sequence of the intron identified by a method of theinvention is described by the nucleotide sequences 5′-CURAY-3′ (SEQ IDNO. 75) or 5″-YURAY-3′ (SEQ ID NO. 76), wherein the U and A areessential nucleotides, and purines and pyrimidines are preferrednucleotides at positions 3 and 5 respectively. In position 1,pyrimidines are preferred but also C is preferred to U. The sequencecontext of the 5′ splice-site surrounding the GT dinucleotide may vary.Preferred are 5′ splice-sites of the sequence 5′-RR/GT(RT)(RT)(GY)-3′(SEQ ID NO. 77), wherein R stands for the nucleotides G or A, Y standsfor the nucleotides C or T. The nucleotides given in brackets describingalternative nucleotides at the respective position.

In a preferred embodiment of the invention, the adenine/thymine (AT)content of an inventive intron over the entire sequence is at least 50%,more preferably at least 55%, even more preferably at least 60%.

In a preferred embodiment of the invention the populations of plantintrons to which the inventive methods will be applied comprises a)substantially all introns of a plant genome represented in a DNAsequence database or b) a plant genomic DNA library. In an additionalembodiment of the invention, the population of introns to which theinventive methods will be applied to is selected from the groupconsisting of a) introns located between two protein encoding exons, andb) introns located within the 5′ untranslated region of thecorresponding gene. In order to identify an intron with expressionenhancing properties in plants or plant cells located within a codingregion (between two protein encoding exons) or in the 5′ untranslatedregion of a given gene, the coding regions and the 5′ untranslatedregions from a set of genes (e.g., present in a sequence database) canbe screened for the presence of introns located in said regions and theidentified introns are subsequently screened using one of the inventivemethods. Such an in silico identification process using bioinformaticstools known to the persons skilled in the art can be performed byscreening a) specific DNA sequence databases (e.g., containing solelycoding regions or the 5′ untranslated regions), or b) other publiclyaccessible genomic DNA sequences containing databases. In a preferredembodiment of the invention, the introns with expression enhancingproperties located in the 5′ untranslated regions are identified by amethod comprising the steps of:

-   a. identifying a coding sequences within a set of genes present in a    sequence database, and-   b. identifying EST sequences corresponding to the genes identified    under (a), and-   c. comparing said coding sequences and EST sequences with the    genomic sequence of the respective genes, and-   d. selecting EST sequences comprising the 5′ untranslated region,    and-   e. identifying introns located in said 5′ untranslated regions.

Preferably, the steps of retrieving or generating DNA sequences or thegeneration of specific DNA sequence database and screening the same(e.g. using the criteria according to the inventive methods) can beperformed with the aid of appropriate bioinformatic computer algorithmsand appropriate computer devices known to a skilled person. In apreferred embodiment, the introns where selected from a population ofintrons derived from monocotyledonous plants, especially preferred aremonocotyledonous plants selected from the group consisting of the generaHordeum, Avena, Secale, Triticum, Sorghum, Zea, Saccharum and Oryza.

In a furthermore preferred embodiment of the invention, the populationof introns to which the inventive methods will be applied are selectedfrom a population of plant genes representing the 10% fraction (9^(th)decile) of genes with the highest expression rate in a gene expressionanalysis experiment performed using a plant cell, plant tissue or awhole plant.

To allow the determination of gene expression levels, a number ofdifferent techniques have been proposed (Milosavljevic, A. et al. (1996)Genome Res. 6:132-141; Shoemaker, D. et al. (1996) Nature Genet.14:450-456; Sikela, J. M. and Auffray, C. (1993) Nature Genet.3:189-191; Meier-Ewert S. et al. (1998) Nucleic Acids Research26(9):2216-2223). Therefore, a number of different gene expressionanalysis systems could be employed in accordance with the instantinvention, including, but not limited to microarray analysis, “digitalnorthern”, clone distribution analysis of cDNA libraries using the “DNAsequencing by hybridization method” (Strezoska, Z. et al. (1991) Proc.Natl. Acad. Sci. USA 88:10089-10093) and Serial Analysis of GeneExpression (SAGE, Velculescu, V. E. et al. (1995) Science 270:484-487).

By using the cDNA microarray hybridization technology the expressionprofiles of thousands of genes can be monitored at once. The DNA arrayanalysis has become a standard technique in the molecular biologylaboratory for monitoring gene expression. Arrays can be made either bythe mechanical spotting of pre-synthesized DNA products or by the denovo synthesis of oligonucleotides on a solid substrate, usually aderivatized glass slide. Typically arrays are used to detect thepresence of mRNAs that may have been transcribed from different genesand which encode different proteins. The RNA is extracted from manycells, or from a single cell type, then converted to cDNA or cRNA. Thecopies may be “amplified” by (RT-) PCR. Fluorescent tags areenzymatically incorporated into the newly synthesized strands or can bechemically attached to the new strands of DNA or RNA. A cDNA or cRNAmolecule that contains a sequence complementary to one of thesingle-stranded probe sequences will hybridize, or stick, via basepairing to the spot at which the complementary probes are affixed. Thespot will then fluoresce when examined using a microarray scanner.Increased or decreased fluorescence intensity indicates that cells inthe sample have recently transcribed, or ceased transcription, of a genethat contains the probed sequence. The intensity of the fluorescence isproportional to the number of copies of a particular mRNA that werepresent and thus roughly indicates the activity or expression level ofthat gene. Microarrys (and the respective equipment needed to performthe expression analysis experiments) that can be employed in accordancewith the present invention are commercially available. The GeneChipArabidopsis ATH1 Genome Array, produced from Affimetrix (Santa Clara,Calif.), contains more than 22,500 probe sets representing approximately24,000 genes. The array is based on information from the internationalArabidopsis sequencing project that was formally completed in December2000 (affymetrix.com). Thus, the expression rate of the analyzed genescan be ranked (according to the intensity of the fluorescence of therespective genes after the hybridization process) and the genesbelonging to the 10% of genes showing the highest gene expression ratecan be identified by using microarray analysis.

Databases containing microarray expression profiling results arepublicly available via the internet e.g. the Nottingham ArabidopsisStock Center's microarray database or the OSMID (osmotic stressmicroarray information) database. The Nottingham Arabidopsis StockCenter's microarray database containing a wide selection of microarraydata from Affimetrix gene chips (affymetrix.arabidopsis.info). The OSMIDdatabase (osmid.org) contains the results of approximately 100microarray experiments performed at the University of Arizona. Thisincludes analysis of NaCl, cold, and drought treatments of Arabidopsisthaliana, rice (Oryza sativa), barley, (Hordeum vulgaris), ice plant(Mesembryanthemum crystallinum), and corn (Zea mays). Thus, by using theexpression profiles present in sequence/expression databases theexpression rate of genes can be ranked (according to the clonedistribution of the respective cDNA in the library) and genes belongingto the 10% of genes showing the highest (abundance) gene expression ratecan be identified.

“Digital Northern” are generated by partially sequencing thousands ofrandomly selected clones from relevant cDNA libraries. Differentiallyexpressed genes can then be detected from variations in the counts oftheir cognate sequence tags. The sequence tag-based method consists ofgenerating a large number (thousands) of expressed sequence tags (ESTs)from 3′-directed regional non-normalized cDNA libraries. The concept ofa “digital Northern” comparison is the following: a number of tags isreported to be proportional to the abundance of cognate transcripts inthe tissue or cell type used to make the cDNA library. The variation inthe relative frequency of those tags, stored in computer databases, isthen used to point out the differential expression of the correspondinggenes (Okubo et al. 1992; Matsubara and Okubo 1994). The SAGE method isa further development of this technique, which requires only ninenucleotides as a tag, therefore allowing a larger throughput. Thus, theexpression rate of the analyzed genes by using the “digital Northern”method can be ranked (according to the abundance of the tags of therespective gene in the cDNA library) and the genes belonging to the 10%of genes showing the highest (abundance) gene expression rate can beidentified.

Using the “sequencing by hybridization method” described in the U.S.patents U.S. Pat. No. 5,667,972, U.S. Pat. No. 5,492,806, U.S. Pat. No.5,695,940, U.S. Pat. No. 5,972,619, U.S. Pat. No. 6,018,041, U.S. Pat.No. 6,451,996, U.S. Pat. No. 6,309,824 it is possible to perform insilico clone distribution analysis of complete cDNA libraries. Theentire content of said U.S. patents is incorporated by reference. Thistechnology is commercially available and customized experiments can beconducted in collaboration with the company HySeq Inc. To determineclone distribution by using the “sequencing by hybridization method”, or“HySeq-technology” plants are grown under a variety of conditions andtreatments, and then tissues at different developmental stages arecollected. This is done in a strategic manner so the probability ofharvesting all expressible genes in at least one or more of thelibraries is maximized. mRNA is then extracted from each of thecollected samples and used for the library production. The libraries canbe generated from mRNA purified on oligo dT columns. Colonies fromtransformation of the cDNA library into E. coli are randomly picked andplaced into microtiter plates and subsequently spotted DNA onto asurface. The cDNA inserts from each clone from the microtiter plates arePCR amplified and spotted onto a nylon membrane. A battery of 288 ³³⁻Pradiolabeled seven-mer oligonucleotides are then sequentially hybridizedto the membranes. After each hybridization a blot image is capturedduring a phosphorimage scan to generate a profile for each singleoligonucleotide. Absolute identity is maintained by barcoding for imagecassette, filter and orientation within the cassette. The filters arethen treated using relatively mild conditions to strip the bound probesand then returned to the hybridization chambers for another round. Thehybridization and imaging cycle is repeated until the set of 288oligomers is completed. After completion of hybridizations, each spot(representing a cDNA insert) will have recorded the amount of radiosignal generated from each of the 288 seven-mer oligonucleotides. Theprofile of which oligomers bound, and to what degree, to each singlecDNA insert (a spot on the membrane) is defined as the signaturegenerated from that clone. Each clone's signature is compared with allother signatures generated from the same organism to identify clustersof related signatures. This process “sorts” all of the clones from anorganism into so called “clusters” before sequencing. In the clusteringprocess, complex or tissue specific cDNA libraries are “mined” using aseries of 288 seven base-pair oligonucleotides. By collecting data onthe hybridization signature of these oligos, the random set of clones ina library can be sorted into “clusters”. A cluster is indicative for theabundance of each gene in a particular library and is therefore ameasure of the gene expression rate of an individual gene. Thus, theexpression rate of genes can be ranked using the “HySeq” technology andthe genes belonging to the 10% of genes showing the highest (abundance)gene expression rate can be identified.

The genes, cDNAs or expressed sequence tags chosen for theidentification of the inventive introns, belonging to the 10%,preferably 5%, more preferably 3% most preferably 1% of genes showingthe highest gene expression rate in a gene expression analysisexperiment, wherein the gene expression rate can be calculatedindirectly by using the above described methods. In a preferredembodiment of the invention, the nucleic acid sequences of the genesbelonging to the 10% of genes showing the highest gene expression ratewhere used to isolate the complete genomic DNA sequence including theintron sequences—of the respective genes by screening of e.g.appropriate DNA sequences containing databases, or genomic DNA orgenomic DNA libraries using hybridization methods or RACE cloningtechniques (rapid amplification of cDNA ends), or chromosome walkingtechniques. After sequence determination of the isolated completegenomic DNA of the respective candidate gene, the intron sequencespresent in said genes were screened using the above described criteriato identify those introns, having expression enhancing properties. Thedescribed in silico methods for the selection of introns with expressionenhancing properties have a high probability of success, but theefficiency of the described methods may be further increased bycombination with other methods. Therefore, in one preferred embodimentof the invention independent validation of the genes representing the10% of genes showing the highest gene expression rate in a geneexpression analysis experiment is done using alternative gene expressionanalysis tools, like Northern analysis, or real time PCR analysis (seeexamples).

In a preferred embodiment of the invention the method for theidentification or enrichment of introns with gene expression enhancingproperties in plants is applied to DNA sequence databases using anautomated process, more preferably using a computer device and analgorithm that defines the instructions needed for accomplishing theselection steps for identifying or enriching introns with geneexpression enhancing properties in plants within the screened populationof DNA sequences. A further embodiment of the invention is a computeralgorithm that defines the instructions needed for accomplishing theselection steps for identifying or enriching introns with plant geneexpression enhancing properties as described above. Useful computeralgorithms are well known in the art of bioinformatics or computationalbiology. Bioinformatics or computational biology is the use ofmathematical and informational techniques to analyze sequence data (e.g.generation of sequence data, sequence alignments, screening of sequencedata) usually by creating or using computer programs, mathematicalmodels or both. One of the main areas of bioinformatics is the datamining and analysis of data gathered from different sources. Other areasare sequence alignment, protein structure prediction. Another aspect ofbioinformatics in sequence analysis is the automatic search for genes orregulatory sequences within a genome (e.g. intron sequences within astretch of genomic DNA). Sequence databases can be searched using avariety of methods. The most common is probably searching for a sequencesimilar to a certain target gene whose sequence is already known to theuser. A useful program is the BLAST (Basic Local Alignment Search Tool)program a method of this type. BLAST is an algorithm for comparingbiological sequences, such as DNA sequences of different genes. Given alibrary or database of sequences, a BLAST search enables a researcher tolook for specific sequences. The BLAST algorithm and a computer programthat implements it were developed by Stephen Altschul at the U.S.National Center for Biotechnology Information (NCBI) and is available onthe web at ncbi.nlm.nih.gov/BLAST. The BLAST program can either bedownloaded and run as a command-line utility “blastall” or accessed forfree over the web. The BLAST web server, hosted by the NCBI, allowsanyone with a web browser to perform similarity searches againstconstantly updated databases of proteins and DNA that include most ofthe newly sequenced organisms. BLAST is actually a family of programs(all included in the blastall executable) including beside others theNucleotide-nucleotide BLAST (BLASTN). This program, given a DNA query,returns the most similar DNA sequences from the DNA database that theuser specifies. A person skilled in the art knows how to produce orretrieve sequence Data from e.g. public sequence database and to designalgorithms to screen the set of sequences in a customized way (seeexamples).

Additionally, the invention relates to computer algorithm that definesthe instructions needed for accomplishing the selection steps foridentifying or enriching introns with gene expression enhancingproperties in plants from a plant genome or a population of intronsselected from the group consisting of introns located between twoprotein encoding exons, and/or introns located within the 5′untranslated region of the corresponding gene and/or introns located inthe DNA sequences of genes representing the 10% fraction of genes withthe highest expression rate in a gene expression analysis experimentperformed using a plant cell, plant tissue and/or a whole plant. Anotherembodiment of the invention is a computer device or data storage devicecomprising the algorithm. A storage device can be a hard disc” (or “harddrive”) or an optical data storage medium like a CD-ROM (“Compact DiscRead-Only Memory” (ROM) or DVD (digital versatile disc) or any othermechanically, magnetically, or optically data storage medium.

Another embodiment of the invention relates to a method for isolating,providing or producing an intron with gene expression enhancingproperties in plants comprising the steps of

-   a) performing an identification or enrichment of introns with gene    expression enhancing properties in plants as described above and    providing the sequence information of said identified or enriched    introns, and-   b) providing the physical nucleotide sequence of said introns    identified or enriched under a) and-   c) evaluating the gene expression enhancing properties of the intron    sequence provided under b) in an in vivo or in vitro expression    experiment, and-   d) isolating introns from said expression experiment c), which    demonstrate expression enhancing properties.

Preferably, evaluation of the gene expression enhancing properties ofthe isolated introns comprises,

-   c1) providing a recombinant expression constructs by functionally    linking an individual nucleotide sequence from step b) with at least    one promoter sequence functioning in plants or plant cells, and at    least one readily quantifiable nucleic acid sequence, and-   c2) introducing said recombinant DNA expression construct in plant    cells and evaluating the gene expression enhancing properties of the    isolated intron.

Preferably, the evaluation of the gene expression enhancing propertiesis done in a plant cell or stable transformed plants and wherein saidisolated intron enhances expression of a given gene at least twofold(see examples).

An additional subject matter of the invention relates to a recombinantDNA expression construct comprising at least one promoter sequencefunctioning in plants cells, at least one nucleic acid sequence and atleast one intron selected from the group consisting of the sequencesdescribed by SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16,17, 18, 19, 20, 21 and 22, and functional equivalents thereof, whereinsaid promoter sequence and at least one of said intron sequences arefunctionally linked to said nucleic acid sequence and wherein saidintron is heterologous to said nucleic acid sequence or to said promotersequence. Furthermore, the invention relates to recombinant expressionconstructs comprising at least one promoter sequence functioning inplants cells, at least one nucleic acid sequence and at least onefunctional equivalents of an intron described by any of sequences SEQ IDNOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21and 22.

Preferably, said functional equivalents comprising the functionalelements of an intron, wherein said promoter sequence and at least oneof said intron sequences are functionally linked to said nucleic acidsequence and wherein said intron is heterologous to said nucleic acidsequence or to said promoter sequence. More preferably, the functionalequivalent is further characterized by

-   i) having at least 50 consecutive base pairs of the intron sequence    described by any of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13,    14, 15, 16, 17, 18, 19, 20, 21 or 22, or-   ii) having an identity of at least 80% over a sequence of at least    95 consecutive nucleic acid base pairs to a sequences described by    any of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17,    18, 19, 20, 21 or 22 or-   iii) hybridizing under high stringent conditions with a nucleic acid    fragment of at least 50 consecutive base pairs of a nucleic acid    molecule described by any of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11,    12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22,

In a preferred embodiment of the invention, the introns comprising atleast 50 bases pairs, more preferably at least 40 bases pairs, mostpreferably 30 bases pairs of the sequences/exons 5′ and 3′ adjacent tothe 5′ and 3′ splice sites of the intron, respectively. In anotherembodiment of the in, the recombinant DNA expression construct of theinvention further comprises one or more additional regulatory sequencesfunctionally linked to a promoter. Those regulatory sequences can beselected from the group consisting of heat shock-, anaerobicresponsive-, pathogen responsive-, drought responsive-, low temperatureresponsive-, ABA responsive-elements, 5′-untranslated gene region,3′-untranslated gene region, transcription terminators, polyadenylationsignals and enhancers. Cis- and trans-acting factors involved inABA-induced gene expression have been reviewed by Bray (1997) TrendsPlant Sci. 2:48-54; Busk et al. (1998) Plant Mol. Biol. 37:425-435 andShinozaki and Yamaguchi-Shinozaki (2000) Curr. Opin. Plant Biol.3:217-223). Many ABA-inducible genes contain a conserved,ABA-responsive, cis-acting element named ABRE (ABA-responsive element;PyACGTGGC) in their promoter regions (Guiltinan et al. (1990) Science250:267-271; Mundy et al. (1990) Proc. Natl. Acad. Sci. USA 87:406-410).The promoter region of the rd29A gene was analyzed, and a novelcis-acting element responsible for dehydration- and cold-inducedexpression was identified at the nucleotide sequence(Yamaguchi-Shinozaki and Shinozaki (1994) Plant Cell 6:251-264.). A 9-bpconserved sequence, TACCGACAT, termed the dehydration-responsive element(DRE), is essential for the regulation of dehydration responsive geneexpression. DRE-related motifs have been reported in the promoterregions of cold- and drought-inducible genes such as kin1, cor6.6, andrd17 (Wang et al. (1995) Plant Mol. Biol. 28:605-617; Iwasaki et al.(1997) Plant Physiol. 115:1287). The thermoinducibility of the heatshock genes is attributed to activation of heat shock factors (HSF). HSFact through a highly conserved heat shock promoter element (HSE) thathas been defined as adjacent and inverse repeats of the motif5′-nGAAn-3′ (Amin et al. (1988) Mol Cell Biol 8:3761-3769). Examples fordefense or pathogen response elements are the W-box (TTGACY) andW-box-like elements, representing binding sites for plant-specific WRKYtranscription factors involved in plant development and plant responsesto environmental stresses (Eulgem et al. (2000) Trends Plant Sci5:199-206; Robatzek S et al. (2001) Plant J 28:123-133), and theMyc-element (CACATG) (Rushton P J et al. (1998) Curr Opin Plant Biol1:311-315). Such regulatory sequences or elements that can be employedin conjunction with a described promoter, encompass the 5′-untranslatedregions, enhancer sequences and plant polyadenylation signals. Examplesof translation enhancers, which may be mentioned, are the tobacco mosaicvirus 5′ leader sequence (Gallie et al. (1987) Nucl Acids Res15:8693-8711), the enhancer from the octopine synthase gene and thelike. Furthermore, they may promote tissue specificity (Rouster J et al.(1998) Plant J 15:435-440). The recombinant DNA expression constructwill typically include the gene of interest along with a 3′ end nucleicacid sequence that acts as a signal to terminate transcription andsubsequent polyadenylation of the RNA. Preferred plant polyadenylationsignals are those, which essentially correspond to T-DNA polyadenylationsignals from Agrobacterium tumefaciens, in particular gene 3 of theT-DNA (octopine synthase) of the Ti plasmid pTiACHS (Gielen et al.(1984) EMBO J. 3:835-46) or functional equivalents thereof. Examples ofterminator sequences, which are especially suitable, are the OCS(octopin synthase) terminator and the NOS (nopaline synthase)terminator. An expression cassette and the vectors derived from it maycomprise further functional elements. The term functional element is tobe understood in the broad sense and refers to all those elements, whichhave an effect on the generation, amplification or function of theexpression cassettes, vectors or recombinant organisms according to theinvention. The following may be mentioned by way of example, but not bylimitation:

1. Selection Markers

Selection markers are useful to select and separate successfullytransformed or homologous recombined cells. To select cells which havesuccessfully undergone homologous recombination, or else to selecttransformed cells, it is, also typically necessary to introduce aselectable marker, which confers resistance to a biocide (for exampleherbicide), a metabolism inhibitor such as 2-deoxyglucose-6-phosphate(WO 98/45456) or an antibiotic to the cells which have successfullyundergone recombination. The selection marker permits the selection ofthe transformed cells from untransformed ones (McCormick et al. (1986)Plant Cell Reports 5:81-84).

1.1 Negative Selection Markers

Selection markers confer a resistance to a biocidal compound such as ametabolic inhibitor (e.g., 2-deoxyglucose-6-phosphate, WO 98/45456),antibiotics (e.g., kanamycin, G 418, bleomycin or hygromycin) orherbicides (e.g., phosphinothricin or glyphosate). Especially preferrednegative selection markers are those which confer resistance toherbicides. Examples which may be mentioned are:

-   -   Phosphinothricin acetyltransferases (PAT; also named Bialophos        resistance; bar; de Block et al. (1987) EMBO J. 6:2513-2518)

-   5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) confer-ring    resistance to Glyphosate (N-(phosphonomethyl)glycine),

-   Glyphosate degrading enzymes (Glyphosate oxidoreductase; gox),

-   Dalapon inactivating dehalogenases (deh)

-   sulfonylurea- and imidazolinone-inactivating acetolactate synthases    (for example mutated ALS variants with, for example, the S4 and/or    Hra mutation)    -   Bromoxynil degrading nitrilases (bxn)    -   Kanamycin- or G418-resistance genes (NPTII; NPTI) coding e.g.,        for neomycin phosphotransferases,

-   2-Desoxyglucose-6-phosphate phosphatase (DOGR1-Gene product; WO    98/45456; EP 0 807 836) conferring resistance against    2-desoxyglucose (Randez-Gil et al., 1995 Yeast 11:1233-1240).

Additional suitable negative selection marker are the aadA gene, whichconfers resistance to the antibiotic spectinomycin, the streptomycinphosphotransferase (SPT) gene, which allows resistance to streptomycinand the hygromycin phosphotransferase (HPT) gene, which mediatesresistance to hygromycin. Especially preferred are negative selectionmarkers that confer resistance against the toxic effects imposed byD-amino acids like e.g., D-alanine and D-serine (WO 03/060133; Erikson2004). Especially preferred as negative selection marker in this contestare the daol gene (EC: 1.4. 3.3: GenBank Acc. No.: U60066) from theyeast Rhodotorula gracilis (Rhodosporidium toruloides) and the E. coligene dsdA (D-serine dehydratase (D-serine deaminase) [EC: 4.3. 1.18;GenBank Acc. No.: J01603).

1.2) Counter Selection Marker

Counter selection markers are especially suitable to select organismswith defined deleted sequences comprising said marker (Koprek T et al.(1999) Plant J 19(6): 719-726). Examples for counter selection markercomprise thymidin kinases (TK), cytosine deaminases (Gleave A P et al.(1999) Plant Mol. Biol. 40(2):223-35; Perera R J et al. (1993) PlantMol. Biol. 23(4): 793-799; Stougaard J. (1993) Plant J 3:755-761),cytochrom P450 proteins (Koprek et al. (1999) Plant J 16:719-726),haloalkandehalogenases (Naested H (1999) Plant J 18:571-576), iaaH geneproducts (Sundaresan V et al. (1995) Genes & Development 9:1797-1810),cytosine deaminase codA (Schlaman H R M and Hooykaas P J J (1997) PlantJ 11:1377-1385), or tms2 gene products (Fedoroff N V & Smith D L, 1993,Plant J 3:273-289).

1.3 Positive Selection Marker

Furthermore, positive selection marker can be employed. Genes likeisopentenyltransferase from Agrobacterium tumefaciens (strain: PO22;Genbank Acc.-No.: AB025109) may—as a key enzyme of the cytokininbiosynthesis—facilitate regeneration of transformed plants (e.g., byselection on cytokinin-free medium). Corresponding selection methods aredescribed (Ebinuma 2000a,b). Additional positive selection markers,which confer a growth advantage to a transformed plant in comparisonwith a non-transformed one, are described e.g., in EP-A 0 601 092.Growth stimulation selection markers may include (but shall not belimited to) β-Glucuronidase (in combination with e.g., a cytokininglucuronide), mannose-6-phosphate isomerase (in combination withmannose), UDP-galactose-4-epimerase (in combination with e.g.,galactose), wherein mannose-6-phosphate isomerase in combination withmannose is especially preferred.

2) Reporter Genes

Reporter genes encode readily quantifiable proteins and, via their coloror enzyme activity, make possible an assessment of the transformationefficacy, the site of expression or the time of expression. Veryespecially preferred in this context are genes encoding reporterproteins (Schenborn E and Groskreutz D. (1999) Mol. Biotechnol.13(1):29-44) such as the green fluorescent protein (GFP) (Sheen et al.(1995) Plant Journal 8(5):777-784; Haseloff et al. (1997) Proc Natl AcadSci USA 94(6):2122-2127; Reichel et al. (1996) Proc Natl Acad Sci USA93(12):5888-5893; Tian et al. (1997) Plant Cell Rep 16:267-271; WO97/41228; Chui W L et al. (1996) Curr Biol 6:325-330; Leffel S M et al.(1997) Biotechniques. 23(5):912-8), chloramphenicol-transferase, aluciferase (Ow et al. (1986) Science 234:856-859; Millar et al. (1992)Plant Mol Biol Rep 10:324-414), the aequorin gene (Prasher et al. (1985)Biochem Biophys Res Commun 126(3):1259-1268), β-galactosidase, R locusgene (encoding a protein which regulates the production of anthocyaninpigments (red coloring) in plant tissue and thus makes possible thedirect analysis of the promoter activity without addition of furtherauxiliary substances or chromogenic substrates; Dellaporta et al. (1988)In: Chromosome Structure and Function: Impact of New Concepts, 18thStadler Genetics Symposium 11:263-282), with β-glucuronidase being veryespecially preferred (Jefferson et al. (1987) EMBO J. 6:3901-3907).

3) Origins of replication, which ensure amplification of the expressioncassettes or vectors according to the invention in, for example, E.coli. Examples which may be mentioned are ORI (origin of DNAreplication), the pBR322 ori or the P15A ori (Sambrook et al.: MolecularCloning. A Laboratory Manual, 2nd ed. Cold Spring Harbor LaboratoryPress, Cold Spring Harbor, N.Y., 1989).4) Elements which are necessary for Agrobacterium-mediated planttransformation, such as, for example, the right or left border of theT-DNA or the vir region.

The inventive recombinant expression construct contains expressiblenucleic acid sequences in addition to, or other than, nucleic acidsequences encoding for marker proteins. In a preferred embodiment of theinvention the recombinant DNA expression construct comprises an nucleicacid sequence encodes for i) a protein or ii) a sense, antisense, ordouble-stranded RNA sequence. In a further preferred embodiment of thepresent invention, the recombinant DNA expression construct contains anucleic acid sequence encoding a protein. In yet another embodiment ofthe invention the recombinant DNA expression construct may contain a DNAfor the purpose of expressing RNA transcripts that function to affectplant phenotype without being translated into a protein. Such nonprotein expressing sequences comprising antisense RNA molecules, senseRNA molecules, RNA molecules with ribozyme activity, double strandforming RNA molecules (RNAi). The transgenic expression constructs ofthe invention can be employed for suppressing or reducing expression ofendogenous target genes by “gene silencing”. The skilled worker knowspreferred genes or proteins whose suppression brings about anadvantageous phenotype. Examples may include but are not limited todown-regulation of the n-subunit of Arabidopsis G protein for increasingroot mass (Ullah et al. (2003) Plant Cell 15:393-409), inactivatingcyclic nucleotide-gated ion channel (CNGC) for improving diseaseresistance (WO 2001007596), and down-regulation of 4-coumarate-CoAligase (4CL) gene for altering lignin and cellulose contents (US2002138870). In yet another preferred embodiment of the invention, thetransgenic expression constructs of the invention contain nucleic acids,which when transcribed, produce RNA enzymes (Ribozymes) which can act asendonucleases and catalyze the cleavage of RNA molecules with selectedsequences. The cleavage of the selected RNA can result in the reducedproduction of their encoded polypeptide products. Ribozymes havespecific catalytic domains that possess endonuclease activity (Kim andCeck 1987, Proc. Natl. Acad. Sci. USA, 84:8788-8792; Gerlach et al.,1987, Nature, 328:802-805; Forster and Symons, 1987, Cell, 49:211-220).Several different ribozyme motifs have been described with RNA cleavageactivity (Symons, 1992, Annu. Rev. Biochem., 61: 641-671). Examplesinclude sequences from group 1 self splicing introns including TobaccoRingspot Virus (Prody et al., 1986, Science, 231:1577-1580). Othersuitable ribozymes include sequences from RNaseP with cleavage activity(Yan et al. (1992) Proc. Natl. Acad. Sci. USA 87:4144-4148), hairpinribozyme structures (Berzal-Herranz et al. (1992) Genes and Devel.98:1207-1210) and Hepatitis Delta virus based ribozyme (U.S. Pat. No.5,625,047). The general design and optimization of ribozymes directedRNA cleavage activity has been discussed on detail (Haseloff and Gerlach(1988) Nature 224:585-591; Symons (1992) Annu. Rev. Biochem. 61:641-671). The choice of a particular nucleic acid sequence to bedelivered to a host cell or plant depends on the aim of thetransformation. In general, the main goal of producing transgenic plantsis to add some beneficial traits to the plant.

In another embodiment of the invention, the recombinant expressionconstruct comprises a nucleic acid sequence encoding for a selectablemarker protein, a screenable marker protein, a anabolic active protein,a catabolic active protein, a biotic or abiotic stress resistanceprotein, a male sterility protein or a protein affecting plant agronomiccharacteristics. Such traits include, but are not limited to, herbicideresistance or tolerance, insect resistance or tolerance, diseaseresistance or tolerance (viral, bacterial, fungal, nematode); stresstolerance, as exemplified by tolerance to drought, heat, chilling,freezing, salt stress, oxidative stress; increased yield, food content,male sterility, starch quantity and quality, oil content and quality,vitamin content and quality (e.g. vitamin E) and the like. One maydesire to incorporate one or more nucleic acid sequences conferring anyof such desirable traits. Furthermore, the recombinant expressionconstructs of the invention can comprise artificial transcriptionfactors (e.g. of the zinc finger protein type; Beerli (2000) Proc NatlAcad Sci USA 97(4):1495-500). These factors attach to the regulatoryregions of the endogenous genes to be expressed or to be repressed and,depending on the design of the factor, bring about expression orrepression of the endogenous gene. The following may be mentioned by wayof example but not by way of limitation as nucleic acid sequences orpolypeptides which can be used for these applications:

Improved protection of the plant embryo against abiotic stresses such asdrought, high or low temperatures, for example by overexpressing theantifreeze polypeptides from Myoxocephalus scorpius (WO 00/00512),Myoxocephalus octodecemspinosus, the Arabidopsis thaliana transcriptionactivator CBF1, glutamate dehydrogenases (WO 97/12983, WO 98/11240), alate embryogenesis gene (LEA), for example from barley (WO 97/13843),calcium-dependent protein kinase genes (WO 98/26045), calcineurins (WO99/05902), farnesyl transferases (WO 99/06580, Pei 1998), ferritin (Deak1999), oxalate oxidase (WO 99/04013; Dunwell 1998), DREB1A factor(dehydration response element B 1A; Kasuga 1999), mannitol or trehalosesynthesis genes, such as trehalose-phosphate synthase ortrehalose-phosphate phosphatase (WO 97/42326), or by inhibiting genessuch as the trehalase gene (WO 97/50561). Especially preferred nucleicacids are those which encode the transcriptional activator CBF1 fromArabidopsis thaliana (GenBank Acc. No.: U77378) or the Myoxocephalusoctodecemspinosus antifreeze protein (GenBank Acc. No.: AF306348), orfunctional equivalents of these. For expression in plants, the nucleicacid molecule must be linked operably to a suitable promoter. The plantspecific promoter, regulatory element and the terminator of theinventive recombinant expression construct needs not be of plant origin,and may originate from viruses or microorganisms, in particular forexample from viruses which attack plant cells.

An additional subject matter of the invention is the introduction of aninventive intron sequence into a target nucleic acid sequence viahomologous recombination (HR). As a prerequisite for the HR between therecombinant expression construct and the genomic target nucleic acidsequence, the recombinant expression construct must contain fragments ofthe target nucleic acid sequence of sufficient length and homology. In apreferred embodiment of the invention, the intron sequences that has tobe inserted into the gene of interest via HR is (within the recombinantexpression construct) placed between a pair of DNA sequences identicalto the region 5′ and 3′ to the preferred place of insertion. In thiscase, the recombinant expression construct can comprises only the intronsequence and the nucleic acid sequences needed to induce the HR event.In a preferred embodiment of the invention, the intron sequence that isflanked by the nucleic acid sequence of the target DNA, contains anexpression cassette that enables the expression of an selectable markerprotein which allows the selection of transgenic plants in which ahomologues or illegitimate recombination had occurred subsequent to thetransformation. The expression cassette driving the expression of theselection marker protein can be flanked by HR control sequences that arerecognized by specific endonucleases or recombinases, facilitating theremoval of the expression cassette from the genome. Such so calledmarker excision methods e.g. the cre/lox technology permit atissue-specific, if appropriate inducible, removal of the expressioncassette from the genome of the host organism (Sauer B (1998) Methods.14(4):381-92). In this method, specific flanking sequences (loxsequences), which later allow removal by means of cre recombinase, areattached to the target gene.

Specifically, the present invention relates to transgenic expressioncassettes comprising the following introns with gene expressionenhancing properties in plants:

1) The sequence of the first intron (BPSI.1, SEQ ID NO: 1) isolated fromthe Oryza sativa metallothioneine-like gene (Gene Bank accession No.AP002540, Oryza sativa (Japonica cultivar group) genomic DNA, Chromosome1, PAC clone: P0434B04, gene_id=“P0434B04.31, protein_id=“BAB44010.1”,complement joined sequences: 142304 . . . 142409, 143021 . . . 143098,143683 . . . 143747; Hsieh, H. M. et al., RNA expression patterns of atype 2 metallothioneine-like gene from rice. Plant Mol. Biol. 32 (3),525-529 (1996)). The gene comprises two introns and three exons. Thefirst intron of the Oryza sativa metallothioneine-like gene (BPSI.1, SEQID NO:1) is flanked by the 5′ (5′-GU-3′, base pair (bp) 1-2 in SEQ IDNO:1) and 3′ (5′-CAG-3′, bp 582-584 in SEQ ID NO:1) splice sites. In apreferred embodiment of the invention, the first intron of the Oryzasativa metallothioneine-like gene (BPSI.1, SEQ ID NO:1) comprises atleast 28 bases pairs, more preferably at least 40 bases pairs, mostpreferably at least 50 base pairs of the sequences 5′ and 3′ adjacent tothe 5′ and 3′ splice sites of the intron, respectively (SEQ ID NO: 82).On nucleotide level, the Oryza sativa metallothionein-like gene shareshigh homology or identity with the coding region of orthologous genesfrom other monocotyledonous or dicotyledonous plants e.g. 89% identityto the Zea mays CL1155_(—)3 mRNA sequence (acc. No. AY109343), 88%identity to the Poa secunda metallothionein-like protein type 2 mRNA(acc. No. AF246982.1), 93% identity to the Triticum aestivummetallothioneine mRNA, partial coding sequence (acc. No. AF470355.1),89% identity to the Nicotiana plumbaginifolia metallothionein-likeprotein mRNA (acc. No. NPU35225), 86% identity to the Brassica oleraceacultivar Green King metallothioneine-like protein 2 (acc. No. AF200712),95% and 88% identity to the Hordeum vulgare subsp. vulgare partial mRNAfor metallothioneine type2 mt2b (acc. No. HVU511346) and mtb2a (acc. No.HVU511345) genes, respectively (identities have been calculated usingthe BLASTN 2.2.9 algorithm [May 1, 2004] Altschul, Stephen F. et al.,(1997), Gapped BLAST and PSI-BLAST: a new generation of protein databasesearch programs, Nucleic Acids Res. 25:3389-3402).

2) The sequence of the first intron (BPSI.2, SEQ ID NO:2) isolated fromthe Oryza sativa Sucrose UDP Glucosyltransferase-2 gene (Gene Bankaccession No. AC084380, Oryza sativa (Japonica cultivar group) genomicDNA, chromosome 3, BAC OSJNBa0090P23, gene ID=“OSJNBa0090P23.15”,Protein ID=AAK5219.1, complement join (nucleotide 62884 to. 65255,65350.65594, 65693.66011, 66098.66322, 66427.66593, 66677.66793,66881.67054, 67136.67231, 67316.67532, 67652.67770, 67896.68088,68209.68360, 68456.68585, 69314.69453 and 70899.72082). The genecomprises 13 introns and 14 exons. The first intron of the Oryza sativaSucrose UDP Glucosyltransferase-2 gene (BPSI.2, SEQ ID NO: 2) is flankedby the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:2) and 3′ (5′-CAG-3′, bp726-728 in SEQ ID NO: 2) splice sites. In a preferred embodiment of theinvention, the first intron of the Oryza sativa Sucrose UDPGlucosyltransferase-2 gene (SEQ ID NO:2) comprises at least 19 basespairs of the sequence 5′ to the 5′-splice site and 23 bases pairs of thesequences/exons 3′ to the 3′-splice site of the intron (SEQ ID NO: 83).In a particularly preferred embodiment the intron BPSI.2 comprises atleast 40 bases pairs, more preferably at least 50 bases pairs of thesequences 5′ and 3′ adjacent to the 5′ and 3′ splice sites of theintron, respectively

3) The sequence of the second intron isolated from the Oryza sativaSucrose UDP Glucosyltransferase-2 gene (BPSI.3, SEQ ID NO:3). Said thesecond intron is flanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:3) and3′ (5′-CAG-3′, bp 93-95 in SEQ ID NO: 3) splice sites.

In a preferred embodiment of the invention, the second intron of theOryza sativa Sucrose UDP Glucosyltransferase-2 gene (SEQ ID NO:3)comprises at least 25 bases pairs of the sequence 5′ to the 5′-splicesite and 30 bases pairs of the sequences 3′ to the 3′-splice site of theintron (SEQ ID NO: 84). In a particularly preferred embodiment theintron BPSI.3 comprises at least 40 bases pairs, more preferably atleast 50 bases pairs of the sequences 5′ and 3′ adjacent to the 5′ and3′ splice sites of the intron, respectively. On nucleotide level, theOryza sativa Sucrose UDP Glucosyltransferase-2 gene shares high homologyor identity with the coding region of orthologous genes from othermonocotyledonous or dicotyledonous plants e.g. 88% identity to the Zeamays sucrose synthase (Sus1) mRNA (acc. No. L22296.1), 85% identity tothe Triticum aestivum mRNA for sucrose synthase type 2 (acc. No.AJ000153), 85% identity to the H. vulgare mRNA for sucrose synthase (accNo. X69931), 80% identity to the Saccharum officinarum sucrosesynthase-2 mRNA (acc No. AF263384.1), 95% identity to the Rice mRNA forsucrose synthase (S464 gene), partial sequence (acc. No. D10418), 79%identity to the Glycine max sucrose synthase mRNA (acc. No. AF03231).Identities have been calculated using the BLASTN 2.2.9 algorithm [May 1,2004] Altschul, Stephen F. et al., (1997), Gapped BLAST and PSI-BLAST: anew generation of protein database search programs, Nucleic Acids Res.25:3389-3402).

4) The sequence of the eighth intron (BPSI.5, SEQ ID NO:5) isolated fromthe Oryza sativa gene encoding for the Sucrose transporter (Gene Bankaccession No. AF 280050). Said the eighth intron (SEQ ID NO:5) isflanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:5) and 3′ (5′-CAG-3′,bp 223-225 in SEQ ID NO: 5) splice sites. In a preferred embodiment ofthe invention, the eighth intron of the Oryza sativa gene encoding forthe Sucrose transporter (SEQ ID NO:5) comprises at least 35 bases pairsof the sequence 5′ to the 5″-splice site and 30 bases pairs of thesequences 3′ to the 3′-splice site of the intron (SEQ ID NO: 86). In aparticularly preferred embodiment the intron BPSI.5 comprises at least40 bases pairs, more preferably at least 50 bases pairs of the sequences5′ and 3′ adjacent to the 5′ and 3′ splice sites of the intron,respectively. In a more preferred embodiment, the 5′ and 3′ splice sitesof the eighth intron (BPSI.5, SEQ ID NO:5) are modified in order tomatch the plant consensus sequences for 5′ splice sites 5′-AG::GTAAGT-3′(SEQ ID NO: 80) and 3′ splice sites 5′-CAG::GT-3′ (SEQ ID NO: 81) usinga PCR mutagenesis approach (SEQ ID NO:87).

5) The sequence of the fourth intron (BPSI.6, SEQ ID NO:6) isolated fromthe Oryza sativa gene (Gene Bank accession No. BAA94221) encoding for anunknown protein with homology to the A. thaliana chromosome II sequencefrom clones T22O13, F12K2 encoding for a putative lipase (AC006233).Said the fourth intron (SEQ ID NO:6) is flanked by the 5′ (5′-GU-3′, by1-2 in SEQ ID NO:6) and 3′ (5′-CAG-3′, by 768-770 in SEQ ID NO:6) splicesites. In a preferred embodiment of the invention, the fourth intron ofthe Oryza sativa gene (accession No. BAA94221) (SEQ ID NO:6) comprisesat least 34 bases pairs of the sequence 5′ to the 5′-splice site and 34bases pairs of the sequences 3′ to the 3′-splice site of the intron (SEQID NO: 88). In a particularly preferred embodiment the intron BPSI.6comprises at least 40 bases pairs, more preferably at least 50 basespairs of the sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sitesof the intron, respectively. In a more preferred embodiment, the 5′ and3′ splice sites of fourth intron (BPSI.6, SEQ ID NO:6) are modified inorder to match the plant consensus sequences for 5′ splice sites5′-AG::GTAAGT-3′ (SEQ ID NO: 80) and 3′ splice sites 5′-CAG::GT-3′ (SEQID NO: 81) using a PCR mutagenesis approach (SEQ ID NO:89).

6) The sequence of the fourth intron (BPSI.7, SEQ ID NO:7) isolated fromthe Oryza sativa gene (accession No. BAB90130) encoding for a putativecinnamyl-alcohol dehydrogenase. Said the fourth intron (SEQ ID NO:7) isflanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:7) and 3′ (5′-CAG-3′,713-715 by in SEQ ID NO: 7) splice sites. In a preferred embodiment ofthe invention, the fourth intron of the Oryza sativa gene (accession No.BAB90130) (SEQ ID NO:7) comprises at least 34 bases pairs of thesequence 5′ to the 5″-splice site and 26 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 90). In a particularlypreferred embodiment the intron BPSI.7 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.In a more preferred embodiment, the 5′ and 3′ splice sites of the fourthintron (BPSI.7, SEQ ID NO:7) are modified in order to match the plantconsensus sequences for 5′ splice sites 5′-AG::GTAAGT-3′ (SEQ ID NO: 80)and 3′ splice sites 5′-CAG::GT-3′ (SEQ ID NO: 81) using a PCRmutagenesis approach (SEQ ID NO:91).

7) The sequence of the third intron (BPSI.10, SEQ ID NO:10) isolatedfrom the Oryza sativa gene (accession No. AP003300) encoding for aputative protein kinase. Said the third intron (SEQ ID NO:10) is flankedby the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:10) and 3′ (5′-CAG-3′, 536-538by in SEQ ID NO: 10) splice sites. In a preferred embodiment of theinvention, the third intron of the Oryza sativa gene (accession No.AP003300) (SEQ ID NO:10) comprises at least 31 bases pairs of thesequence 5′ to the 5′-splice site and 31 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 94). In a particularlypreferred embodiment the intron BPSI.10 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.In a more preferred embodiment, the 5′ and 3′ splice sites of the thirdintron (BPSI.10, SEQ ID NO:10) are modified in order to match the plantconsensus sequences for 5′ splice sites 5′-AG::GTAAGT-3′ (SEQ ID NO: 80)and 3′ splice sites 5″-CAG::GT-3′ (SEQ ID NO: 81) using a PCRmutagenesis approach (SEQ ID NO:95).

8) The sequence of the first intron (BPSI.11, SEQ ID NO:11) isolatedfrom the Oryza sativa gene (accession No. L37528) encoding for a MADS3box protein. Said the first intron (SEQ ID NO:11) is flanked by the 5′(5′-GU-3′, by 1-2 in SEQ ID NO:11) and 3′ (5′-CAG-3′, by 329-331 in SEQID NO: 11) splice sites. In a preferred embodiment of the invention, thefirst intron of the Oryza sativa gene (accession No. L37528) (SEQ IDNO:11) comprises at least 35 bases pairs of the sequence 5′ to the5′-splice site and 34 bases pairs of the sequences 3′ to the 3′-splicesite of the intron (SEQ ID NO: 96). In a particularly preferredembodiment the intron BPSI.11 comprises at least 40 bases pairs, morepreferably at least 50 bases pairs of the sequences 5′ and 3′ adjacentto the 5′ and 3′ splice sites of the intron, respectively. In a morepreferred embodiment, the 5′ and 3′ splice sites of the first intron(BPSI.11, SEQ ID NO:11) are modified in order to match the plantconsensus sequences for 5′ splice sites 5′-AG::GTAAGT-3′ (SEQ ID NO: 80)and 3′ splice sites 5″-CAG::GT-3′ (SEQ ID NO: 81) using a PCRmutagenesis approach (SEQ ID NO:97).

9) The sequence of the first intron (BPSI.12, SEQ ID NO:12) isolatedfrom the Oryza sativa gene (accession No. CB625805) encoding for aputative Adenosylmethionine decarboxylase. Said the first intron (SEQ IDNO:12) is flanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:12) and 3′(5′-CAG-3′, by 959-961 in SEQ ID NO: 12) splice sites. In a preferredembodiment of the invention, the first intron of the Oryza sativa gene(accession No. CB625805) (SEQ ID NO:12) comprises at least 26 basespairs of the sequence 5′ to the 5′-splice site and 26 bases pairs of thesequences 3′ to the 3′-splice site of the intron (SEQ ID NO: 98). In aparticularly preferred embodiment the intron BPSI.12 comprises at least40 bases pairs, more preferably at least 50 bases pairs of the sequences5′ and 3′ adjacent to the 5′ and 3′ splice sites of the intron,respectively.

10) The sequence of the first intron (BPSI.13, SEQ ID NO:13) isolatedfrom the Oryza sativa gene (accession No. CF297669) encoding for anAspartic proteinase. Said the first intron (SEQ ID NO:13) is flanked bythe 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:13) and 3′ (5′-CAG-3′, by 593-595in SEQ ID NO: 13) splice sites. In a preferred embodiment of theinvention, the first intron of the Oryza sativa gene (accession No.CF297669) (SEQ ID NO:13) comprises at least 26 bases pairs of thesequence 5′ to the 5′-splice site and 24 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 99). In a particularlypreferred embodiment the intron BPSI.13 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.

11) The sequence of the first intron (BPSI.14, SEQ ID NO:14) isolatedfrom the Oryza sativa gene (accession No. CB674940) encoding for aLec14b protein. Said the first intron (SEQ ID NO:14) is flanked by the5′ (5′-GU-3′, by 1-2 in SEQ ID NO:14) and 3′ (5′-CAG-3′, by 143-145 inSEQ ID NO: 14) splice sites. In a preferred embodiment of the invention,the first intron of the Oryza sativa gene (accession No. CB674940) (SEQID NO:14) comprises at least 26 bases pairs of the sequence 5′ to the5′-splice site and 25 bases pairs of the sequences 3′ to the 3′-splicesite of the intron (SEQ ID NO: 100). In a particularly preferredembodiment the intron BPSI.14 comprises at least 40 bases pairs, morepreferably at least 50 bases pairs of the sequences 5′ and 3′ adjacentto the 5′ and 3′ splice sites of the intron, respectively.

12) The sequence of the first intron (BPSI.15, SEQ ID NO:15) isolatedfrom the 5′ UTR of the Oryza sativa gene (accession No. BAD37295.1)encoding for a putative SalT protein precursor. Said the first intron(SEQ ID NO:15) is flanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:15)and 3′ (5′-CAG-3′, by 312-314 in SEQ ID NO: 15) splice sites. In apreferred embodiment of the invention, the first intron of the Oryzasativa gene (accession No. BAD37295.1) (SEQ ID NO:15) comprises at least26 bases pairs of the sequence 5′ to the 5′-splice site and 25 basespairs of the sequences 3′ to the 3′-splice site of the intron (SEQ IDNO: 101). In a particularly preferred embodiment the intron BPSI.15comprises at least 40 bases pairs, more preferably at least 50 basespairs of the sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sitesof the intron, respectively.

13) The sequence of the first intron (BPSI.16, SEQ ID NO:16) isolatedfrom the Oryza sativa gene (accession No. BX928664) encoding for aputative reticulon. Said the first intron (SEQ ID NO:16) is flanked bythe 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:16) and 3′ (5′-CAG-3′, by 650-652in SEQ ID NO: 16) splice sites. In a preferred embodiment of theinvention, the first intron of the Oryza sativa gene (accession No.BX928664) (SEQ ID NO:16) comprises at least 26 bases pairs of thesequence 5′ to the 5′-splice site and 23 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 102). In a particularlypreferred embodiment the intron BPSI.16 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.

14) The sequence of the first intron (BPSI.17, SEQ ID NO:17) isolatedfrom the Oryza sativa gene (accession No. AA752970) encoding for aglycolate oxidase. Said the first intron (SEQ ID NO:17) is flanked bythe 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:17) and 3′ (5′-CAG-3′, by 266-268in SEQ ID NO:17) splice sites. In a preferred embodiment of theinvention, the first intron of the Oryza sativa gene (accession No.AA752970) (SEQ ID NO:17) comprises at least 26 bases pairs of thesequence 5′ to the 5′-splice site and 35 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 103). In a particularlypreferred embodiment the intron BPSI.17 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.

15) The sequence of the first intron (BPSI.18, SEQ ID NO:18) isolatedfrom the Oryza sativa clone GI 40253643 (accession No. AK064428) issimilar to AT4g33690. Said the first intron (SEQ ID NO:18) is flanked bythe 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:18) and 3′ (5′-CAG-3′, by 544-546in SEQ ID NO:18) splice sites. In a preferred embodiment of theinvention, the first intron of the Oryza sativa gene (accession No.AK064428) (SEQ ID NO:18) comprises at least 26 bases pairs of thesequence 5′ to the 5′-splice site and 21 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 104). In a particularlypreferred embodiment the intron BPSI.18 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.

16) The sequence of the first intron (BPSI.19, SEQ ID NO:19) isolatedfrom the Oryza sativa clone GI 51091887 (accession No. AK062197)). Saidthe first intron (SEQ ID NO:19) is flanked by the 5′ (5′-GU-3′, by 1-2in SEQ ID NO:19) and 3′ (5′-CAG-3′, by 810-812 in SEQ ID NO:19) splicesites. In a preferred embodiment of the invention, the first intron ofthe Oryza sativa gene (accession No. AK062197) (SEQ ID NO:19) comprisesat least 26 bases pairs of the sequence 5′ to the 5′-splice site and 26bases pairs of the sequences 3′ to the 3′-splice site of the intron (SEQID NO: 105). In a particularly preferred embodiment the intron BPSI.19comprises at least 40 bases pairs, more preferably at least 50 basespairs of the sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sitesof the intron, respectively.

17) The sequence of the first intron (BPSI.20, SEQ ID NO:20) isolatedfrom the Oryza sativa gene (accession No. CF279761) encoding for ahypothetical protein clone (GI 33657147). Said the first intron (SEQ IDNO:20) is flanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:20) and 3′(5′-CAG-3′, by 369-371 in SEQ ID NO:20) splice sites. In a preferredembodiment of the invention, the first intron of the Oryza sativa gene(accession No. CF279761) (SEQ ID NO:20) comprises at least 26 basespairs of the sequence 5′ to the 5″-splice site and 27 bases pairs of thesequences 3′ to the 3′-splice site of the intron (SEQ ID NO: 106). In aparticularly preferred embodiment the intron BPSI.20 comprises at least40 bases pairs, more preferably at least 50 bases pairs of the sequences5′ and 3′ adjacent to the 5′ and 3′ splice sites of the intron,respectively.

18) The sequence of the first intron (BPSI.21, SEQ ID NO:21) isolatedfrom the Oryza sativa gene (accession No. CF326058) encoding for aputative membrane transporter. Said the first intron (SEQ ID NO:21) isflanked by the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:21) and 3′ (5′-CAG-3′,by 720-722 in SEQ ID NO:21) splice sites. In a preferred embodiment ofthe invention, the first intron of the Oryza sativa gene (accession No.CF326058) (SEQ ID NO:21) comprises at least 26 bases pairs of thesequence 5′ to the 5′-splice site and 25 bases pairs of the sequences 3′to the 3′-splice site of the intron (SEQ ID NO: 107). In a particularlypreferred embodiment the intron BPSI.21 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.

The sequence of the first intron (BPSI.22, SEQ ID NO:22) isolated fromthe Oryza sativa gene (accession No. C26044) encoding for a putative ACTdomain repeat protein. Said the first intron (SEQ ID NO:22) is flankedby the 5′ (5′-GU-3′, by 1-2 in SEQ ID NO:22) and 3′ (5′-CAG-3′, by386-388 in SEQ ID NO:22) splice sites. In a preferred embodiment of theinvention, the first intron of the Oryza sativa gene (accession No.C26044) (SEQ ID NO:22) comprises at least 26 bases pairs of the sequence5′ to the 5′-splice site and 28 bases pairs of the sequences 3′ to the3′-splice site of the intron (SEQ ID NO: 108). In a particularlypreferred embodiment the intron BPSI.22 comprises at least 40 basespairs, more preferably at least 50 bases pairs of the sequences 5′ and3′ adjacent to the 5′ and 3′ splice sites of the intron, respectively.

TABLE 1 Genes from which the introns of the invention are preferablyisolated, putative function of said genes, cDNA and the protein encodedby said genes. Rice GI Accesion SEQ Intron number No. ID NO. Sequencehomology BPSI.1 AP002540 1 metallothioneine-like gene BPSI.2 AC084380 2Sucrose UDP Glucosyl- transferase-2 gene, first Intron BPSI.3 AC084380 3Sucrose UDP Glucosyl- transferase-2 gene, second Intron BPSI.4 AC0843804 Sucrose UDP Glucosyl- transferase-2 gene, third Intron BPSI.5 9624451AF280050 5 Sucrose transporter BPSI.6 7523493 BAA94221 6 Similar to A.thaliana chromosome II sequence from clones T22O13, F12K2; putativelipase (AC006233) BPSI.7 20161203 BAB90130 7 putative cinnamyl-alcoholdehydrogenase BPSI.10 20160990 AP003300 10 Putative protein kinaseBPSI.11 886404 L37528 11 MADS3 box protein BPSI.12 29620794 CB625805 12putative Adenosyl- methionine decarboxylase BPSI.13 33666702 CF297669 13Aspartic proteinase BPSI.14 29678665 CB674940 14 Lec14b protein BPSI.1551535011 BAD37295 15 putative SalT protein precursor BPSI.16 41883853BX928664 16 Putative Reticulon BPSI.17 2799981 AA752970 17 Glycolateoxidase BPSI.18 40253643 AK06442 18 Putative non-coding (Similar toAT4g33690) BPSI.19 51091887 AK062197 19 Putative non-coding BPSI.2033657147 CF279761 20 Hypothetical protein BPSI.21 33800379 CF326058 21Putative membrane transporter BPSI.22 2309889 C26044 22 Putative ACTdomain repeat protein

It is disclosed by the examples of this invention, that the inventiveintrons with the SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10 and 11 have an impacton the expression rate of the GUS gene in transient expression assaysand stable transformed plants, respectively. It could be shown that theinclusion of said Introns into the 5′ UTR of the GUS gene has led to astrong enhancement in the expression rate of this gene in transientlyand stable transformed cell, respectively, compared to a controlconstruct that lacks the first intron (see examples 1.6.1 (table 7),1.6.2 (table 8), 2.4 (table 15).

The expression enhancing properties of the introns with the SEQ ID NOs:12, 13, 14, 15, 16, 17, 18, 19, 20, 21 or 22 can be demonstrated byperforming the above described transient or stable expression assays.

Functional equivalents of the inventive introns can be identified viahomology searches in nucleic acid databases or via DNA hybridization(screening of genomic DNA libraries) using a fragment of at least 50consecutive base pairs of the nucleic acid molecule described by any ofthe SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21 or 22 and stringent hybridization conditions. In a preferredembodiment of the present invention the stringent hybridizing conditionscan be chosen as follows:

The hybridization puffer contains Formamide, NaCl and PEG 6000(Polyethyleneglykol MW 6000). Formamide has a destabilizing effect ondouble strand nucleic acid molecules, thereby, when used inhybridization buffer, allowing the reduction of the hybridizationtemperature to 42° C. without reducing the hybridization stringency.NaCl has a positive impact on the renaturation-rate of a DNA duplex andthe hybridization efficiency of a DNA probe with its complementary DNAtarget. PEG increases the viscosity of the hybridization buffer, whichhas in principle a negative impact on the hybridization efficiency. Thecomposition of the hybridization buffer is as follows:

250 mM Sodium phosphate-buffer pH 7.2 1 mM EDTA(ethylenediaminetetraacetic acid) 7% SDS (g/v) (sodium dodecyl sulfate)250 mM NaCl (Sodiumchloride) 10 μg/ml single stranded DNA 5%Polyethylenglykol (PEG) 6000 40% Formamide

The hybridization is preferably performed over night at 42° C. In themorning, the hybridized filter will be washed 3× for 10 minutes with2×SSC+0.1% SDS. Hybridization should advantageously be carried out withfragments of at least 50, 60, 70 or 80 bp, preferably at least 90 bp. Inan especially preferred embodiment, the hybridization should be carriedout with the entire nucleic acid sequence with conditions describedabove.

Combination of the introns of the invention with different plantpromoters has clearly demonstrated their expression enhancing and/ormodulating properties. In a preferred embodiment of the invention therecombinant DNA expression construct comprises (functionally linked toan intron of the invention) a promoter sequence functioning in plants orplant cells selected from the group consisting of

-   a) the rice chloroplast protein 12 (Os.CP12) promoter as described    by nucleotide 1 to 854 of SEQ ID NO: 113 (the “fragment”), or a    sequence having at least 60% (preferably at least 70% or 80%, more    preferably at least 90% or 95%, most preferably at least 98% or 99%)    identity to said fragment, or a sequence hybridizing under stringent    conditions (preferably under conditions equivalent to the high    stringency conditions defined in the paragraph above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment, and-   b) the maize hydroxyproline-rich glycoprotein (Zm.HRGP) promoter as    described by nucleotide 1 to 1184 of SEQ ID NO: 114, or a sequence    having at least 60% (preferably at least 70% or 80%, more preferably    at least 90% or 95%, most preferably at least 98% or 99%) identity    to said fragment, or a sequence hybridizing under stringent    conditions (preferably under conditions equivalent to the high    stringency conditions defined in the paragraph above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment, and-   c) the rice p-caffeoyl-CoA 3-O-methyltransferase (Os.CCoAMT1)    promoter as described by nucleotide 1 to 1034 of SEQ ID NO: 115, or    a sequence having at least 60% (preferably at least 70% or 80%, more    preferably at least 90% or 95%, most preferably at least 98% or 99%)    identity to said fragment, or a sequence hybridizing under stringent    conditions (preferably under conditions equivalent to the high    stringency conditions defined in the paragraph above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment, and-   d) the maize Globulin-1 (Zm.Glb1) promoter (W64A) as described by    nucleotide 1 to 1440 of SEQ ID NO: 116, or a sequence having at    least 60% (preferably at least 70% or 80%, more preferably at least    90% or 95%, most preferably at least 98% or 99%) identity to said    fragment, or a sequence hybridizing under stringent conditions    (preferably under conditions equivalent to the high stringency    conditions defined in the paragraph above) to said fragment, or a    sequence comprising at least 50 (preferably at least 100, more    preferably at least 200 or 300, most preferably at least 400 or 500)    consecutive nucleotides of said fragment, and-   e) the putative Rice H+-transporting ATP synthase (Os.V-ATPase)    promoter as described by nucleotide 1 to 1589 of SEQ ID NO: 117, or    a sequence having at least 60% (preferably at least 70% or 80%, more    preferably at least 90% or 95%, most preferably at least 98% or 99%)    identity to said fragment, or a sequence hybridizing under stringent    conditions (preferably under conditions equivalent to the high    stringency conditions defined in the paragraph above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment, and-   f) the putative rice C-8,7 sterol isomerase (Os.C8,7 SI) promoter as    described by nucleotide 1 to 796 of SEQ ID NO: 118, or a sequence    having at least 60% (preferably at least 70% or 80%, more preferably    at least 90% or 95%, most preferably at least 98% or 99%) identity    to said fragment, or a sequence hybridizing under stringent    conditions (preferably under conditions equivalent to the high    stringency conditions defined in the paragraph above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment, and-   g) the maize lactate dehydrogenase (Zm.LDH) promoter as described by    nucleotide 1 to 1062 of SEQ ID NO: 119, or a sequence having at    least 60% (preferably at least 70% or 80%, more preferably at least    90% or 95%, most preferably at least 98% or 99%) identity to said    fragment, or a sequence hybridizing under stringent conditions    (preferably under conditions equivalent to the high stringency    conditions defined in the paragraph above) to said fragment, or a    sequence comprising at least 50 (preferably at least 100, more    preferably at least 200 or 300, most preferably at least 400 or 500)    consecutive nucleotides of said fragment, and-   h) the rice Late Embryogenesis Abundant (Os.Lea) promoter as    described by nucleotide 1 to 1386 of SEQ ID NO: 121, or a sequence    having at least 60% (preferably at least 70% or 80%, more preferably    at least 90% or 95%, most preferably at least 98% or 99%) identity    to said fragment, or a sequence hybridizing under stringent    conditions (preferably under conditions equivalent to the high    stringency conditions defined in the paragraph above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment.

Preferably said expression construct is comprising a combination of oneof the above defined promoters with at least one intron selected fromthe group consisting of

-   i) the BPSI.1 intron as described by nucleotide 888 to 1470 of SEQ    ID NO: 113 or a sequence having at least 60% (preferably at least    70% or 80%, more preferably at least 90% or 95%, most preferably at    least 98% or 99%) identity to said fragment, or a sequence    hybridizing under stringent conditions (preferably under conditions    equivalent to the high stringency conditions defined above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment and-   ii) the BPSI.5 intron as described by nucleotide 1068 to 1318 of SEQ    ID NO: 120, or a sequence having at least 60% (preferably at least    70% or 80%, more preferably at least 90% or 95%, most preferably at    least 98% or 99%) identity to said fragment, or a sequence    hybridizing under stringent conditions (preferably under conditions    equivalent to the high stringency conditions defined above) to said    fragment, or a sequence comprising at least 50 (preferably at least    100, more preferably at least 200 or 300, most preferably at least    400 or 500) consecutive nucleotides of said fragment.

More preferably expression construct is comprising a combination ofpromoter and intron selected from the group consisting of

-   i) sequences as described by any of SEQ ID NO: 113, 114, 115, 116,    117, 118, 119, 120, or 121, and-   ii) sequences having at least 50 (preferably at least 100, more    preferably at least 200 or 300, most preferably at least 400 or 500)    consecutive nucleotides of a sequence described by any of SEQ ID    NOs: 113, 114, 115, 116, 117, 118, 119, 120, or 121, and-   iii) sequences having an identity of at least 60% (preferably at    least 70% or 80%, more preferably at least 90% or 95%, most    preferably at least 98% or 99%) to a sequence described by any of    SEQ ID NOs: 113, 114, 115, 116, 117, 118, 119, 120, or 121, and-   iv) sequences hybridizing under stringent conditions (preferably    under conditions equivalent to the high stringency conditions    defined above) with sequence described by any of SEQ ID NOs: 113,    114, 115, 116, 117, 118, 119, 120, or 121.

A preferred subject matter of the invention, is a vector, preferably aplant transformation vector, containing an inventive recombinantexpression construct. The expression cassette can be introduced into thevector via a suitable restriction cleavage site. The plasmid formed isfirst introduced into E. coli. Correctly transformed E. coli areselected, grown, and the recombinant plasmid is obtained by the methodsfamiliar to the skilled worker. Restriction analysis and sequencing mayserve to verify the cloning step. Preferred vectors are those, whichmake possible stable integration of the expression cassette into thehost genome. An expression construct according to the invention canadvantageously be introduced into cells, preferably into plant cells,using vectors. In one embodiment, the methods of the invention involvetransformation of organism or cells (e.g. plants or plant cells) with atransgenic expression vector comprising at least a transgenic expressioncassette of the invention. The methods of the invention are not limitedto the expression vectors disclosed herein. Any expression vector whichis capable of introducing a nucleic acid sequence of interest into aplant cell is contemplated to be within the scope of this invention.Typically, expression vectors comprise the transgenic expressioncassette of the invention in combination with elements which allowcloning of the vector into a bacterial or phage host. The vectorpreferably, though not necessarily, contains an origin of replicationwhich is functional in a broad range of prokaryotic hosts. A selectablemarker is generally, but not necessarily, included to allow selection ofcells bearing the desired vector. Preferred are those vectors thatallowing a stable integration of the expression construct into the hostgenome. In the case of injection or electroporation of DNA into plantcells, the plasmid used need not meet any particular requirements.Simple plasmids such as those of the pUC series can be used. If intactplants are to be regenerated from the transformed cells, it is necessaryfor an additional selectable marker gene to be present on the plasmid. Avariety of possible plasmid vectors are available for the introductionof foreign genes into plants, and these plasmid vectors contain, as arule, a replication origin for multiplication in E. coli and a markergene for the selection of transformed bacteria. Examples are pBR322, pUCseries, M13mp series, pACYC184 and the like. The expression constructcan be introduced into the vector via a suitable restriction cleavagesite. The plasmid formed is first introduced into E. coli. Correctlytransformed E. coli are selected and grown, and the recombinant plasmidis obtained by methods known to the skilled worker. Restriction analysisand sequencing can be used for verifying the cloning step.

Depending on the method by which DNA is introduced, further genes may benecessary on the vector plasmid.

Agrobacterium tumefaciens and A. rhizogenes are plant-pathogenic soilbacteria, which genetically transform plant cells. The Ti and Riplasmids of A. tumefaciens and A. rhizogenes, respectively, carry genesresponsible for genetic transformation of the plant (Kado (1991) Crit.Rev Plant Sci 10:1). Vectors of the invention may be based on theAgrobacterium Ti- or Ri-plasmid and may thereby utilize a natural systemof DNA transfer into the plant genome. As part of this highly developedparasitism Agrobacterium transfers a defined part of its genomicinformation (the T-DNA; flanked by about 25 by repeats, named left andright border) into the chromosomal DNA of the plant cell (Zupan (2000)Plant J 23(1):11-28). By combined action of the so-called vir genes(part of the original Ti-plasmids) said DNA-transfer is mediated. Forutilization of this natural system, Ti-plasmids were developed whichlack the original tumor inducing genes (“disarmed vectors”). In afurther improvement, the so called “binary vector systems”, the T-DNAwas physically separated from the other functional elements of theTi-plasmid (e.g., the vir genes), by being incorporated into a shuttlevector, which allowed easier handling (EP-A 120 516; U.S. Pat. No.4,940,838). These binary vectors comprise (beside the disarmed T-DNAwith its border sequences), prokaryotic sequences for replication bothin Agrobacterium and E. coli. It is an advantage ofAgrobacterium-mediated transformation that in general only the DNAflanked by the borders is transferred into the genome and thatpreferentially only one copy is inserted. Descriptions of Agrobacteriumvector systems and methods for Agrobacterium-mediated gene transfer areknown in the art (Miki 1993, “Procedures for Introducing Foreign DNAinto Plants” in METHODS IN PLANT MOLECULAR BIOLOGY AND BIOTECHNOLOGY;pp. 67-88; Gruber 1993, “Vectors for Plant Transformation,” in METHODSIN PLANT MOLECULAR BIOLOGY AND BIOTECHNOLOGY; pp. 89-119; Moloney (1989)Plant Cell Reports 8: 238-242). The use of T-DNA for the transformationof plant cells has been studied and described intensively (EP 120516;Hoekema 1985, In: The Binary Plant Vector System, OffsetdrukkerijKanters B. V., Alblasserdam, Chapter V; Fraley (1985) CRC Crit. Rev.Plant. Sci. 4:1-45; and An (1985) EMBO J. 4:277-287). Various binaryvectors are known, some of which are commercially available such as, forexample, pBIN19 (Clontech Laboratories, Inc. U.S.A.). Hence, forAgrobacterium-mediated transformation the transgenic expressionconstruct of the invention is integrated into specific plasmids, eitherinto a shuttle or intermediate vector, or into a binary vector. If a Tior Ri plasmid is to be used for the transformation, at least the rightborder, but in most cases the right and left border, of the Ti or Riplasmid T-DNA is linked to the transgenic expression construct to beintroduced in the form of a flanking region. Binary vectors arepreferably used. Binary vectors are capable of replication both in E.coli and in Agrobacterium. They may comprise a selection marker gene anda linker or polylinker (for insertion of e.g. the expression constructto be transferred) flanked by the right and left T-DNA border sequence.They can be transferred directly into Agrobacterium (Holsters (1978) MolGen Genet. 163:181-187). The selection marker gene permits the selectionof transformed agrobacteria and is, for example, the nptII gene, whichconfers resistance to kanamycin. The Agrobacterium which acts as hostorganism in this case should already contain a plasmid with the virregion. The latter is required for transferring the T-DNA to the plantcell. An Agrobacterium transformed in this way can be used fortransforming plant cells. The use of T-DNA for transforming plant cellshas been studied and described intensively (EP 120 516; Hoekema (1985)Nature 303:179-181; An (1985) EMBO J. 4:277-287; see also below). Commonbinary vectors are based on “broad host range”-plasmids like pRK252(Bevan (1984) Nucl Acid Res 12:8711-8720) or pTJS75 (Watson (1985) EMBOJ. 4(2):277-284) derived from the P-type plasmid RK2. Most of thesevectors are derivatives of pBIN19 (Bevan 1984, Nucl Acid Res12:8711-8720). Various binary vectors are known, some of which arecommercially available such as, for example, pB1101.2 or pBIN19(Clontech Laboratories, Inc. USA). Additional vectors were improved withregard to size and handling (e.g. pPZP; Hajdukiewicz (1994) Plant MolBiol 25:989-994). Improved vector systems are described also in WO02/00900. In a preferred embodiment, Agrobacterium strains for use inthe practice of the invention include octopine strains, e.g., LBA4404 oragropine strains, e.g., EHA101 or EHA105. Suitable strains of A.tumefaciens for DNA transfer are for example EHA101pEHA101 (Hood (1986)J Bacteriol 168:1291-1301), EHA105[pEHA105] (Li (1992) Plant Mol Biol20:1037-1048), LBA4404[pAL4404] (Hoekema (1983) Nature 303:179-181),C58C1[pMP90] (Koncz (1986) Mol Gen Genet. 204:383-396), andC58C1[pGV2260] (Deblaere (1985) Nucl Acids Res 13:4777-4788. Othersuitable strains are Agrobacterium tumefaciens C58, a nopaline strain.Other suitable strains are A. tumefaciens C58C1 (Van Larebeke (1974)Nature 252:169-170, A136 (Watson (1975) J. Bacteriol 123:255-264) orLBA4011 (Klapwijk (1980) J. Bacteriol. 141:128-136 In a preferredembodiment, the Agrobacterium strain used to transform the plant tissuepre-cultured with the plant phenolic compound contains aL,L-succinamopine type Ti-plasmid, preferably disarmed, such as pEHA101.In another preferred embodiment, the Agrobacterium strain used totransform the plant tissue pre-cultured with the plant phenolic compoundcontains an octopine-type Ti-plasmid, preferably disarmed, such aspAL4404. Generally, when using octopine-type Ti-plasmids or helperplasmids, it is preferred that the virF gene be deleted or inactivated(Jarchow (1991) Proc. Natl. Acad. Sci. USA 88:10426-10430). In apreferred embodiment, the Agrobacterium strain used to transform theplant tissue pre-cultured with the plant phenolic compound such asacetosyringone. The method of the invention can also be used incombination with particular Agrobacterium strains, to further increasethe transformation efficiency, such as Agrobacterium strains wherein thevir gene expression and/or induction thereof is altered due to thepresence of mutant or chimeric virA or virG genes (e.g. Hansen (1994)Proc. Natl. Acad. Sci. USA 91:7603-7607; Chen 1991 J. Bacteriol.173:1139-1144; Scheeren-Groot (1994) J. Bacteriol 176:6418-6426). Abinary vector or any other vector can be modified by common DNArecombination techniques, multiplied in E. coli, and introduced intoAgrobacterium by e.g., electroporation or other transformationtechniques (Mozo (1991) Plant Mol. Biol. 16:917-918). Agrobacterium isgrown and used as described in the art. The vector comprisingAgrobacterium strain may, for example, be grown for 3 days on YP medium(5 g/L yeast extract, 10 g/L peptone, 5 g/L Nail, 15 g/L agar, pH 6.8)supplemented with the appropriate antibiotic (e.g., 50 mg/Lspectinomycin). Bacteria are collected with a loop from the solid mediumand resuspended.

An additional subject matter of the invention relates to transgenicnon-human organisms transformed with at least one vector containing atransgenic expression construct of the invention. In a preferredembodiment the invention relates to bacteria, fungi, yeasts, morepreferably to plants or plant cell. In a preferred embodiment of theinvention, the transgenic organism is a monocotyledonous plant. In a yetmore preferred embodiment, the monocotyledonous plant is selected fromthe group consisting of the genera Hordeum, Avena, Secale, Triticum,Sorghum, Zea, Saccharum and Oryza, very especially preferred are plantsselected from the group consisting of Hordeum vulgare, Triticumaestivum, Triticum aestivum subsp. spelta, Triticale, Avena sativa,Secale cereale, Sorghum bicolor, Saccharum officinarum, Zea mays andOryza sativa transformed with the inventive vectors or containing theinventive recombinant expression constructs. Preferred bacteria arebacteria of the genus Escherichia, Erwinia, Agrobacterium,Flavobacterium, Alcaligenes or cyanobacteria, for example of the genusSynechocystis. Especially preferred are microorganisms which are capableof infecting plants and thus of transferring the constructs according tothe invention. Preferred microorganisms are those from the genusAgrobacterium and, in particular, the species Agrobacterium tumefaciens.Preferred yeasts are Candida, Saccharomyces, Hansenula or Pichia.Preferred fungi are Aspergillus, Trichoderma, Ashbya, Neurospora,Fusarium, Beauveria or other fungi. Plant organisms are furthermore, forthe purposes of the invention, other organisms which are capable ofphotosynthetic activity such as, for example, algae or cyanobacteria,and also mosses. Preferred algae are green algae such as, for example,algae of the genus Haematococcus, Phaedactylum tricomatum, Volvox orDunaliella. Furthermore the invention relates cell cultures, tissues,organs (e.g., leaves, roots and the like in the case of plantorganisms), or propagation material derived from transgenic non-humanorganisms like bacteria, fungi, yeasts, plants or plant cellstransformed with at least one vector containing a transgenic expressionconstruct of the invention.

An additional subject matter of the invention relates to a method forproviding an expression cassette for enhanced expression of a nucleicacid in a plant or a plant cell, comprising the step of functionallylinking the inventive introns to a plant expression cassette notcomprising said intron. In a yet another preferred embodiment, theinvention relates to a method for enhancing the expression of a nucleicacid sequence in a plant or a plant cell, comprising functionallylinking the inventive introns to said nucleic acid sequence. Preferably,the method for providing an expression cassette for enhanced expressionof a nucleic acid in a plant or a plant cell and the method forenhancing the expression of a nucleic acid sequence in a plant or aplant cell further comprises the steps of

-   i) providing an recombinant expression cassette, wherein the nucleic    acid sequence is functionally linked with a promoter sequence    functional in plants and with an intron sequence selected from the    group consisting of SEQ ID NOs: 1, 2, 3, 5, 6, 7, 10, 11, 12, 13,    14, 15, 16, 17, 18, 19, 20, 21 and 22,-   ii) introducing said recombinant expression into a plant cell or a    plant,-   iii) identifying or selecting the transgenic plant cell comprising    said transgenic expression construct. In another preferred    embodiment, the above-described method further comprises the steps    of-   iv) regenerating transgenic plant tissue from the transgenic plant    cell. In an alternative preferred embodiment, the method further    comprises-   v) regenerating a transgenic plant from the transgenic plant cell.

The generation of a transformed organism or a transformed cell requiresintroducing the DNA in question into the host cell in question. Amultiplicity of methods is available for this procedure, which is termedtransformation (see also Keown (1990) Methods in Enzymology185:527-537). For example, the DNA can be introduced directly bymicroinjection or by bombardment via DNA-coated microparticles. Also,the cell can be permeabilized chemically, for example using polyethyleneglycol, so that the DNA can enter the cell by diffusion. The DNA canalso be introduced by protoplast fusion with other DNA-containing unitssuch as minicells, cells, lysosomes or liposomes. Another suitablemethod of introducing DNA is electroporation, where the cells arepermeabilized reversibly by an electrical pulse. Methods forintroduction of a transgenic expression construct or vector into planttissue may include but are not limited to, e.g., electroinjection (Nan(1995) In “Biotechnology in Agriculture and Forestry,” Ed. Y. P. S.Bajaj, Springer-Verlag Berlin Heidelberg 34:145-155; Griesbach (1992)Hort Science 27:620); fusion with liposomes, lysosomes, cells, minicellsor other fusible lipid-surfaced bodies (Fraley (1982) Proc. Natl. Acad.Sci. USA 79:1859-1863); polyethylene glycol (Krens (1982) Nature296:72-74); chemicals that increase free DNA uptake; transformationusing virus, and the like. Furthermore, the biolistic method with thegene gun, electroporation, incubation of dry embryos in DNA-containingsolution, and microinjection may be employed. Protoplast based methodscan be employed (e.g., for rice), where DNA is delivered to theprotoplasts through liposomes, PEG, or electroporation (Shimamoto (1989)Nature 338:274-276; Datta (1990) Bio/Technology 8:736-740).Transformation by electroporation involves the application of short,high-voltage electric fields to create “pores” in the cell membranethrough which DNA is taken-up. These methods are—for example—used toproduce stably transformed monocotyledonous plants (Paszkowski (1984)EMBO J. 3:2717-2722; Shillito (1985) Bio/Technology, 3:1099-1103; Fromm(1986) Nature 319:791-793) especially from rice (Shimamoto (1989) Nature338:274-276; Datta (1990) Bio/Technology 8:736-740; Hayakawa (1992) ProcNatl Acad Sci USA 89:9865-9869). Particle bombardment or “biolistics” isa widely used method for the transformation of plants, especiallymonocotyledonous plants. In the “biolistics” (microprojectile-mediatedDNA delivery) method microprojectile particles are coated with DNA andaccelerated by a mechanical device to a speed high enough to penetratethe plant cell wall and nucleus (WO 91/02071). The foreign DNA getsincorporated into the host DNA and results in a transformed cell. Thereare many variations on the “biolistics” method (Sanford (1990)Physiologia Plantarium 79:206-209; Fromm (1990) Bio/Technology8:833-839; Christou (1988) Plant Physiol 87:671-674; Sautter (1991)Bio/Technology 9:1080-1085). The method has been used to produce stablytransformed monocotyledonous plants including rice, maize, wheat,barley, and oats (Christou (1991) Bio/Technology 9:957-962; Gordon-Kamm(1990) Plant Cell 2:603-618; Vasil (1992) Bio/Technology 10:667-674,(1993) Bio/Technology 11:1153-1158; Wan (1994) Plant Physiol. 104:3748;Somers (1992) Bio/Technology 10:1589-1594). In addition to these“direct” transformation techniques, transformation can also be effectedby bacterial infection by means of Agrobacterium tumefaciens orAgrobacterium rhizogenes. These strains contain a plasmid (Ti or Riplasmid) which is transferred to the plant following Agrobacteriuminfection. Part of this plasmid, termed T-DNA (transferred DNA), isintegrated into the genome of the plant cell (see above for descriptionof vectors). To transfer the DNA to the plant cell, plant explants arecocultured with a transgenic Agrobacterium tumefaciens or Agrobacteriumrhizogenes. Starting from infected plant material (for example leaf,root or stem sections, but also protoplasts or suspensions of plantcells), intact plants can be generated using a suitable medium which maycontain, for example, antibiotics or biocides for selecting transformedcells. The plants obtained can then be screened for the presence of theDNA introduced, in this case the expression construct according to theinvention. As soon as the DNA has integrated into the host genome, thegenotype in question is, as a rule, stable and the insertion in questionis also found in the subsequent generations. The plants obtained can becultured and hybridized in the customary fashion. Two or moregenerations should be grown in order to ensure that the genomicintegration is stable and hereditary. The abovementioned methods aredescribed (for example, in Jenes (1983) Techniques for Gene Transfer,in: Transgenic Plants, Vol. 1, Engineering and Utilization, edited byKung & Wu, Academic Press 128-143; and in Potrykus (1991) Ann Rev PlantPhysiol Plant Mol Biol 42:205-225). One of skill in the art knows thatthe efficiency of transformation by Agrobacterium may be enhanced byusing a number of methods known in the art. For example, the inclusionof a natural wound response molecule such as acetosyringone (AS) to theAgrobacterium culture has been shown to enhance transformationefficiency with Agrobacterium tumefaciens (Shahla (1987) Plant Mol.Biol. 8:291-298). Alternatively, transformation efficiency may beenhanced by wounding the target tissue to be transformed. Wounding ofplant tissue may be achieved, for example, by punching, maceration,bombardment with microprojectiles, etc. (see, e.g., Bidney (1992) PlantMolec. Biol. 18:301-313). A number of other methods have been reportedfor the transformation of plants (especially monocotyledonous plants)including, for example, the “pollen tube method” (WO 93/18168; Luo(1988) Plant Mol. Biol. Rep. 6:165-174), macro-injection of DNA intofloral tillers (Du (1989) Genet Manip Plants 5:8-12), injection ofAgrobacterium into developing caryopses (WO 00/63398), and tissueincubation of seeds in DNA solutions (Topfer (1989) Plant Cell1:133-139). Direct injection of exogenous DNA into the fertilized plantovule at the onset of embryogenesis was disclosed in WO 94/00583. WO97/48814 disclosed a process for producing stably transformed fertilewheat and a system of transforming wheat via Agrobacterium based onfreshly isolated or pre-cultured immature embryos, embryogenic callusand suspension cells.

As a rule, the expression construct integrated contains a selectionmarker, which imparts a resistance to a biocide (for example aherbicide) or an antibiotic such as kanamycin, G 418, bleomycin,hygromycin or phosphinotricin and the like to the transformed plant. Theselection marker permits the selection of transformed cells fromuntransformed cells (McCormick 1986) Plant Cell Reports 5:81-84). Theplants obtained can be cultured and hybridized in the customary fashion.Two or more generations should be grown in order to ensure that thegenomic integration is stable and hereditary. The abovementioned methodsare described (for example, in Jenes 1983; and in Potrykus 1991). Assoon as a transformed plant cell has been generated, an intact plant canbe obtained using methods known to the skilled worker. Accordingly, thepresent invention provides transgenic plants. The transgenic plants ofthe invention are not limited to plants in which each and every cellexpresses the nucleic acid sequence of interest under the control of thepromoter sequences provided herein. Included within the scope of thisinvention is any plant which contains at least one cell which expressesthe nucleic acid sequence of interest (e.g., chimeric plants). It ispreferred, though not necessary, that the transgenic plant comprises thenucleic acid sequence of interest in more than one cell, and morepreferably in one or more tissue. Once transgenic plant tissue, whichcontains an expression vector, has been obtained, transgenic plants maybe regenerated from this transgenic plant tissue using methods known inthe art. Species from the following examples of genera of plants may beregenerated from transformed protoplasts: Fragaria, Lotus, Medicago,Onobrychis, Trifolium, Trigonella, Vigna, Citrus, Linum, Geranium,Manihot, Daucus, Arabidopsis, Brassica, Raphanus, Sinapis, Atropa,Capsicum, Hyoscyamus, Lycopersicon, Nicotiana, Solanum, Petunia,Digitalis, Majorana, Ciohorium, Helianthus, Lactuca, Bromus, Asparagus,Antirrhinum, Hererocallis, Nemesia, Pelargonium, Panicum, Pennisetum,Ranunculus, Senecio, Salpiglossis, Cucumis, Browaalia, Glycine, Pisum,Lolium, Zea, Triticum, Sorghum, and Datura. For regeneration oftransgenic plants from transgenic protoplasts, a suspension oftransformed protoplasts or a Petri plate containing transformed explantsis first provided. Callus tissue is formed and shoots may be inducedfrom callus and subsequently rooted. Alternatively, somatic embryoformation can be induced in the callus tissue. These somatic embryosgerminate as natural embryos to form plants. The culture media willgenerally contain various amino acids and plant hormones, such as auxinand cytokinins. It is also advantageous to add glutamic acid and prolineto the medium, especially for such species as corn and alfalfa.Efficient regeneration will depend on the medium, on the genotype, andon the history of the culture. These three variables may be empiricallycontrolled to result in reproducible regeneration. Plants may also beregenerated from cultured cells or tissues. Dicotyledonous plants whichhave been shown capable of regeneration from transformed individualcells to obtain transgenic whole plants include, for example, apple(Malus pumila), blackberry (Rubus), Blackberry/raspberry hybrid (Rubus),red raspberry (Rubus), carrot (Daucus carota), cauliflower (Brassicaoleracea), celery (Apium graveolens), cucumber (Cucumis sativus),eggplant (Solanum melongena), lettuce (Lactuca sativa), potato (Solanumtuberosum), rape (Brassica napus), wild soybean (Glycine canescens),soybean (Glycine max), strawberry (Fragaria ananassa), tomato(Lycopersicon esculentum), walnut (Juglans regia), melon (Cucumis meio),grape (Vitis vinifera), and mango (Mangifera indica). Monocotyledonousplants which have been shown capable of regeneration from transformedindividual cells to obtain transgenic whole plants include, for example,rice (Oryza sativa), rye (Secale cereale), and maize (Zea mays).

In addition, regeneration of whole plants from cells (not necessarilytransformed) has also been observed in: apricot (Prunus armeniaca),asparagus (Asparagus officinalis), banana (hybrid Musa), bean (Phaseolusvulgaris), cherry (hybrid Prunus), grape (Vitis vinifera), mango(Mangifera indica), melon (Cucumis melo), ochra (Abelmoschusesculentus), onion (hybrid Allium), orange (Citrus sinensis), papaya(Carrica papaya), peach (Prunus persica), plum (Prunus domestica), pear(Pyrus communis), pineapple (Ananas comosus), watermelon (Citrullusvulgaris), and wheat (Triticum aestivum). The regenerated plants aretransferred to standard soil conditions and cultivated in a conventionalmanner. After the expression vector is stably incorporated intoregenerated transgenic plants, it can be transferred to other plants byvegetative propagation or by sexual crossing. For example, invegetatively propagated crops, the mature transgenic plants arepropagated by the taking of cuttings or by tissue culture techniques toproduce multiple identical plants. In seed propagated crops, the maturetransgenic plants are self crossed to produce a homozygous inbred plantwhich is capable of passing the transgene to its progeny by Mendelianinheritance. The inbred plant produces seed containing the nucleic acidsequence of interest. These seeds can be grown to produce plants thatwould produce the selected phenotype. The inbred plants can also be usedto develop new hybrids by crossing the inbred plant with another inbredplant to produce a hybrid.

Confirmation of the transgenic nature of the cells, tissues, and plantsmay be performed by PCR analysis, antibiotic or herbicide resistance,enzymatic analysis and/or Southern blots to verify transformation.Progeny of the regenerated plants may be obtained and analyzed to verifywhether the transgenes are heritable. Heritability of the transgene isfurther confirmation of the stable transformation of the transgene inthe plant. The resulting plants can be bred in the customary fashion.Two or more generations should be grown in order to ensure that thegenomic integration is stable and hereditary. Corresponding methods aredescribed, (Jenes 1993; Potrykus 1991).

Also in accordance with the invention are cells, cell cultures, tissues,parts, organs, such as, for example, roots, leaves and the like in thecase of transgenic plant organisms derived from the above-describedtransgenic organisms, and transgenic propagation material such as seedsor fruits.

Preferably, the method for enhancing the expression of a nucleic acidsequence in a plant or a plant cell further comprises,

linking the introns with expression enhancing properties to theexpression cassette by insertion via homologous recombination comprisingthe following steps:

-   a) providing in vivo or in vitro a DNA construct comprising said    introns flanked by sequences allowing homologous recombination into    a pre-existing expression cassette between the promoter and the    nucleic acid of said expression cassette,-   b) transforming a recipient plant cell comprising said cassette,    regenerating a transgenic plant where said intron has been inserted    into the genomic DNA of said promoter nucleic acid construct via    homologous recombination.

Two different ways for the integration of DNA molecules into genomes arepossible: Either regions of sequence identity between the partners areused (homologous recombination (HR), “gene targeting”) or nosequence-specific requirements have to be fulfilled (illegitimaterecombination also referred to as non-homologous end joining (NHEJ)).Gene targeting (GT) is the generation of specific mutations in a genomeby homologous recombination-mediated integration of foreign DNAsequences. In contrast to natural recombination processes, one of therecombination partners is artificial and introduced by transformation ingene targeting. The integration of transformed DNA follows pre-existingrecombination pathways. Homologous recombination is a reaction betweenany pair of DNA sequences having a similar sequence of nucleotides,where the two sequences interact (recombine) to form a new recombinantDNA species. The frequency of homologous recombination increases as thelength of the shared nucleotide DNA sequences increases, and is higherwith linearized plasmid molecules than with circularized plasmidmolecules. Homologous recombination can occur between two DNA sequencesthat are less than identical, but the recombination frequency declinesas the divergence between the two sequences increases. Introduced DNAsequences can be targeted via homologous recombination by linking a DNAmolecule of interest to sequences sharing homology with endogenoussequences of the host cell. Once the DNA enters the cell, the twohomologous sequences can interact to insert the introduced DNA at thesite where the homologous genomic DNA sequences were located. Therefore,the choice of homologous sequences contained on the introduced DNA willdetermine the site where the introduced DNA is integrated via homologousrecombination. For example, if the DNA sequence of interest is linked toDNA sequences sharing homology to a single copy gene of a host plantcell, the DNA sequence of interest will be inserted via homologousrecombination at only that single specific site. However, if the DNAsequence of interest is linked to DNA sequences sharing homology to amulticopy gene of the host eucaryotic cell, then the DNA sequence ofinterest can be inserted via homologous recombination at each of thespecific sites where a copy of the gene is located. For example, if onewishes to insert a foreign gene into the genomic site where a selectedgene is located, the introduced DNA should contain sequences homologousto the selected gene. A double recombination event can be achieved byflanking each end of the DNA sequence of interest (the sequence intendedto be inserted into the genome) with DNA sequences homologous to theselected gene. A homologous recombination event involving each of thehomologous flanking regions will result in the insertion of the foreignDNA. Thus only those DNA sequences located between the two regionssharing genomic homology become integrated into the genome.

In the case of gene targeting via homologous recombination, theinventive intron that has to be introduced in the chromosome, preferablyin the 5′UTR of a gene (a pre-existing expression cassette), is (forexample) located on a DNA construct and is 5′ and 3′ flanked by nucleicacid sequences of sufficient homology to the target DNA (such anconstruct is called “gene targeting substrate”) in which the intronshould be integrated. Said flanking regions must be sufficient in lengthfor making possible recombination. They are, as a rule, in the range ofseveral hundred bases to several kilo bases in length (Thomas K R andCapecchi M R (1987) Cell 51:503; Strepp et al. (1998) Proc Natl Acad SciUSA 95(8):4368-4373). In a preferred embodiment of the invention, thegene targeting substrate comprises an selection marker that isco-integrated with the intron into the genomic region of interest,allowing the selection of recombination events. Preferably, the genetargeting substrate is integrated via a double cross over event betweenpairs of homologous DNA sequences of sufficient length and homologyresulting in the insertion of the intron sequence (and if desiredadditional nucleic acid sequences e.g. selection marker). Usinghomologous recombination, a intron of the invention can be placed in the5′ non coding region of the target gene (e.g., an endogenous plant gene)to be transgenically expressed, by linking said intron to DNA sequenceswhich are homologous to, for example, endogenous sequences upstreamand/or downstream of the reading frame of the target gene. After a cellhas been transformed with the DNA construct in question, the homologoussequences can interact and thus place the intron of the invention at thedesired site so that the intron sequence of the invention becomesoperably linked to the target gene and constitutes an expressionconstruct of the invention. For homologous recombination or genetargeting, the host organism—for example a plant—is transformed with therecombination construct using the methods described herein, and clones,which have successfully undergone recombination, are selected, forexample using a resistance to antibiotics or herbicides. If desirable totarget the nucleic acid sequence of interest to a particular locus onthe plant genome, site-directed integration of the nucleic acid sequenceof interest into the plant cell genome may be achieved by, for example,homologous recombination using Agrobacterium-derived sequences.Generally, plant cells are incubated with a strain of Agrobacteriumwhich contains a targeting vector in which sequences that are homologousto a DNA sequence inside the target locus are flanked by Agrobacteriumtransfer-DNA (T-DNA) sequences, as previously described (U.S. Pat. No.5,501,967, the entire contents of which are herein incorporated byreference).

One of skill in the art knows that homologous recombination may beachieved using targeting vectors which contain sequences that arehomologous to any part of the targeted plant gene, whether belonging tothe regulatory elements of the gene, or the coding regions of the gene.Homologous recombination may be achieved at any region of a plant geneso long as the nucleic acid sequence of regions flanking the site to betargeted is known. Gene targeting is a relatively rare event in highereucaryotes, especially in plants. Random integrations into the hostgenome predominate. One possibility of eliminating the randomlyintegrated sequences and thus increasing the number of cell clones witha correct homologous recombination is the use of a sequence-specificrecombination system as described in U.S. Pat. No. 6,110,736, by whichunspecifically integrated sequences can be deleted again, whichsimplifies the selection of events which have integrated successfullyvia homologous recombination.

An efficient variant of gene targeting has been reported for Drosophilamelanogaster (Rong and Golic 2000 Science. 2000 Jun. 16;288(5473):2013-8). In this method the construct for targeting isintegrated into the host genome flanked by two recognition sites of asite-specific recombinase and includes a site for a rare cuttingrestriction endonuclease. By induced expression of the site-specificrecombinase a DNA circle is excised from the genome. This circle is thenlinearized after the restriction enzyme (in this case I-SceI) has beenexpressed resulting in an “activated” DNA molecule with both endshomologous to the target sequence. In the female germ line ofDrosophila, gene targeting occurred in about one out of 500 cells.Selection of gene targeting events from events of illegitimaterecombination can be facilitated by certain combinations of positive andnegative selection techniques (WO 99/20780).

Counter selection is a powerful approach in mammalian and plant systemsto enrich for gene targeting events. In plants the bacterial codA geneas a cell autonomous negative selection marker can be used for selectionin tissue culture (Schlaman and Hooykaas Plant J 11:1377-1385, 1997;Thykjaer et al., Plant Mol. Biol. 1997 November; 35(4):523-30.).Negative selection in plants allowed a more than a thousand-foldsuppression of random integration (Risseeuw et al., Plant J. 1997 April;11(4):717-28.; Gallego et al., Plant Mol. Biol. 1999 January;39(1):83-93; Terada et al., Nat. Biotechnol. 2002 October;20(10):1030-4. Epub 2002 Sep. 9.). Exploratory approaches to increasegene targeting in plants comprise expression of proteins like RecA (WO97/08331) or RecA-homologues derived from other species like e.g., Rad52(WO 01/68882) or RecA/VirE2 fusion-proteins (WO 01/38504). Use ofpoly(ADPribose)polymerase inhibitors has demonstrated an increased HR inplants (Puchta H et al. (1995) Plant J 7:203-210). Initiation ofsequence-unspecific DNA double-strand breaks was also found to increaseefficiency of HR in plants (Puchta H et al. (1995) Plant J 7(2),203-210; Lebel E G et al. (1993) Proc Natl Acad Sci USA 90(2):422-426).However, sequence-unspecific induction of DNA strand breaks isdisadvantageous because of the potential mutagenic effect.Sequence-specific induction of DNA strand-breaks may also increaseefficiency of HR but is limited to artificial scenarios (Siebert R andPuchta H (2002) Plant Cell 14(5):1121-1131).

It is specifically contemplated by the inventors that one could employtechniques for the site-specific integration or excision oftransformation constructs prepared in accordance with the instantinvention. An advantage of site-specific integration or excision is thatit can be used to overcome problems associated with conventionaltransformation techniques, in which transformation constructs typicallyrandomly integrate into a host genome in multiple copies. This randominsertion of introduced DNA into the genome of host cells can be lethalif the foreign DNA inserts into an essential gene. In addition, theexpression of a transgene may be influenced by “position effects” causedby the surrounding genomic DNA. Further, because of difficultiesassociated with plants possessing multiple transgene copies, includinggene silencing, recombination and unpredictable inheritance, it istypically desirable to control the copy number of the inserted DNA,often only desiring the insertion of a single copy of the DNA sequence.Site-specific integration or excision of transgenes or parts oftransgenes can be achieved in plants by means of homologousrecombination (see, for example, U.S. Pat. No. 5,527,695). TheDNA-constructs utilized within the method of this invention may compriseadditional nucleic acid sequences. Said sequences may be—forexample—localized in different positions with respect to the homologysequences. Preferably, the additional nucleic acid sequences arelocalized between two homology sequences and may be introduced viahomologous recombination into the chromosomal DNA, thereby resembling aninsertion mutation of said chromosomal DNA. However, the additionalsequences may also be localized outside of the homology sequences (e.g.,at the 5′- or 3′-end of the DNA-construct). In cases where theadditional sequence resembles a counter selection marker this may allowa distinction of illegitimate insertion events from correct insertionevents mediated by homologous recombination. Corresponding negativemarkers are described below and suitable methods are well known in theart (WO 99/20780).

In a preferred embodiment of the invention, efficiency of the method ofthe invention may be further increased by combination with other methodssuitable for increasing homologous recombination. Said methods mayinclude for example expression of HR enhancing proteins (like e.g.,RecA; WO 97/08331; Reiss B et al. (1996) Proc Natl Acad Sci USA93(7):3094-3098; Reiss B et al. (2000) Proc Natl Acad Sci USA97(7):3358-3363) or treatment with PARP inhibitors (Puchta H et al.(1995) Plant J. 7:203-210). Various PARP inhibitors suitable for usewithin this invention are known to the person skilled in the art and mayinclude for example preferably 3-Aminobenzamid,8-Hydroxy-2-methylquinazolin-4-on (NU1025),1,11b-Dihydro-[2H]benzopyrano[4,3,2-de]isoquinolin-3-on (GPI 6150),5-Aminoisoquinolinon,3,4-Dihydro-5-[4-(1-piperidinyl)butoxy]-1(2H)-isoquinolinon or compoundsdescribed in WO 00/26192, WO 00/29384, WO 00/32579, WO 00/64878, WO00/68206, WO 00/67734, WO 01/23386 or WO 01/23390. Furthermore, themethod may be combined with other methods facilitation homologousrecombination and/or selection of the recombinants like e.g.,positive/negative selection, excision of illegitimate recombinationevents or induction of sequence-specific or unspecific DNA double-strandbreaks. In a preferred embodiment, the method for enhancing theexpression of a nucleic acid sequence in a plant or a plant cell furthervia linking the intron with expression enhancing properties to theexpression cassette by insertion via homologous recombination is appliedto monocotyledonous plants or plant cells, more preferably to plantsselected from the group consisting of the genera Hordeum, Avena, Secale,Triticum, Sorghum, Zea, Saccharum, and Oryza, most preferably a maizeplant.

The nucleic acid sequence in which one of the inventive intron isinserted and functionally linked (via the inventive methods), encodesfor a selectable marker protein, a screenable marker protein, a anabolicactive protein, a catabolic active protein, a biotic or abiotic stressresistance protein, a male sterility protein or a protein affectingplant agronomic characteristics as described above and/or a sense,antisense, or double-stranded RNA as described above. In a preferredembodiment of the present invention, said nucleic acid sequence encodesa protein. In yet another embodiment of the invention the method isapplied to recombinant DNA expression construct that contain a DNA forthe purpose of expressing RNA transcripts that function to affect plantphenotype without being translated into a protein. Such non proteinexpressing sequences comprising antisense RNA molecules, sense RNAmolecules, RNA molecules with ribozyme activity, double strand formingRNA molecules (RNAi) as described above.

Additionally, a further subject matter of the invention relates to theuse of the above describes transgenic organism or of cell cultures,parts of transgenic propagation material derived there from, producedwith the inventive method, for the production of foodstuffs, animalfeeds, seeds, pharmaceuticals or fine chemicals. Preferred isfurthermore the use of transgenic organisms for the production ofpharmaceuticals or fine chemicals, where a host organism is transformedwith one of the above-described expression constructs, and thisexpression construct contains one or more structural genes which encodethe desired fine chemical or catalyze the biosynthesis of the desiredfine chemical, the transformed host organism is cultured, and thedesired fine chemical is isolated from the culture medium. This processcan be used widely for fine chemicals such as enzymes, vitamins, aminoacids, sugars, fatty acids, natural and synthetic flavorings, aromasubstances and colorants. Especially preferred is the production oftocopherols and tocotrienols, carotenoids, oils, polyunsaturated fattyacids etc. Culturing the transformed host organisms, and isolation fromthe host organisms or the culture medium, is performed by methods knownto the skilled worker. The production of pharmaceuticals such as, forexample, antibodies, vaccines, enzymes or pharmaceutically activeproteins is described (Hood (1999) Curr Opin Biotechnol. 10(4):382-6; Ma(1999) Curr Top Microbiol. Immunol. 236:275-92; Russel (1999) CurrentTopics in Microbiology and Immunology 240:119-138; Cramer et al. (1999)Current Topics in Microbiology and Immunology 240:95-118; Gavilondo(2000) Biotechniques 29(1):128-138; Holliger (1999) Cancer & MetastasisReviews 18(4):411-419).

Furthermore the present invention relates to recombinant DNA expressionconstruct comprising at least one promoter sequence functioning inplants or plant cells, at least one intron with expression enhancingproperties in plants or plant cells characterized by

-   VIII) an intron length shorter than 1,000 base pairs, and-   IX) presence of a 5′ splice site comprising the dinucleotide    sequence 5′-GT-3′ (SEQ ID NO: 78), and-   X) presence of a 3′ splice site comprising the trinucleotide    sequence 5′-CAG-3′ (SEQ ID NO: 79), and-   XI) presence of a branch point resembling the consensus sequence    5′-CURAY-3′ (SEQ ID NO: 75) upstream of the 3′ splice site, and-   XII) an adenine plus thymine content of at least 40% over 100    nucleotides downstream from the 5′ splice site, and-   XIII) an adenine plus thymine content of at least 50% over 100    nucleotides upstream from the 3′ splice site, and-   XIV) an adenine plus thymine content of at least 55%, and a thymine    content of at least 30% over the entire intron, and

at least one nucleic acid sequence,

wherein said promoter sequence and at least one of said intron sequencesare functionally linked to said nucleic acid sequence and wherein saidintron is heterologous to said nucleic acid sequence and/or to saidpromoter sequence.

Sequences

-   1. SEQ ID NO: 1 BPSI.1: Sequence of the first intron isolated from    the Oryza sativa metallothioneine-like gene (accession No. AP002540)-   2. SEQ ID NO: 2 BPSI.2: Sequence of the first intron isolated from    the Oryza sativa Sucrose UDP Glucosyltransferase-2 gene (accession    No. AC084380)-   3. SEQ ID NO: 3 BPSI.3: Sequence of the second intron isolated from    the Oryza sativa Sucrose UDP Glucosyltransferase-2 gene (accession    No. AC084380)-   4. SEQ ID NO: 4 BPSI.4: Sequence of the third intron isolated from    the Oryza sativa Sucrose UDP Glucosyltransferase-2 gene (accession    No. AC084380)-   5. SEQ ID NO: 5 BPSI.5: Sequence of the eighth intron isolated from    the O. sativa gene encoding for the Sucrose transporter (accession    No. AF 280050).-   6. SEQ ID NO: 6 BPSI.6: Sequence of fourth intron isolated from the    Oryza sativa gene (accession No. BAA94221) encoding for an unknown    protein with homology to the A. thaliana chromosome II sequence from    clones T22013, F12K2 encoding for a putative lipase (AC006233).-   7. SEQ ID NO: 7 BPSI.7: Sequence of the fourth intron isolated from    the Oryza sativa gene (accession No. BAB90130) encoding for a    putative cinnamyl-alcohol dehydrogenase.-   8. SEQ ID NO: 8 BPSI.8: Sequence of the second intron isolated from    the Oryza sativa gene (accession No. AC084766) encoding for a    putative ribonucleoprotein.-   9. SEQ ID NO: 9 BPSI.9: Sequence of the fifth intron isolated from    the Oryza sativa clone GI 12061241.-   10. SEQ ID NO: 10 BPSI.10: Sequence of the third intron isolated    from the O. sativa gene (accession No. AP003300) encoding for a    putative protein kinase.-   11. SEQ ID NO: 11 BPSI.11: Sequence of the first intron isolated    from the O. sativa gene (accession No. L37528) encoding for a MADS3    box protein.-   12. SEQ ID NO: 12 BPSI.12: Sequence of the first intron isolated    from the Oryza sativa gene (accession No. CB625805) encoding for a    putative Adenosylmethionine decarboxylase.-   13. SEQ ID NO: 13 BPSI.13: Sequence of the first intron isolated    from the O. sativa gene (accession No. CF297669) encoding for an    Aspartic proteinase.-   14. SEQ ID NO: 14 BPSI.14: Sequence of the first intron isolated    from the O. sativa gene (accession No. CB674940) encoding for a    Lec14b protein.-   15. SEQ ID NO: 15 BPSI.15: Sequence of the first intron isolated    from the Oryza sativa gene (accession No. BAD37295.1) encoding for a    putative SalT protein precursor-   16. SEQ ID NO: 16 BPSI.16: Sequence of the first intron isolated    from the O. sativa gene (accession No. BX928664) encoding for a    putative Reticulon.-   17. SEQ ID NO: 17 BPSI.17: Sequence of the first intron isolated    from the O. sativa gene (accession No. AA752970) encoding for a    glycolate oxidase.-   18. SEQ ID NO: 18 BPSI.18: Sequence of the first intron isolated    from the Oryza sativa clone (accession No. AK06442 encoding putative    non-coding-   19. SEQ ID NO: 19 BPSI.19: Sequence of the first intron isolated    from the Oryza sativa clone (accession No. AK062197) encoding    putative non-coding-   20. SEQ ID NO: 20 BPSI.20 sequence of the first intron isolated from    the O. sativa gene (accession No. CF279761) encoding for a    hypothetical protein.-   21. SEQ ID NO: 21 BPSI.21 Sequence of the first intron isolated from    the Oryza sativa gene (accession No. CF326058) encoding for a    putative membrane transporter.-   22. SEQ ID NO: 22 BPSI.22: Sequence of the firsit intron isolated    from the Oryza sativa gene (accession No. C26044) encoding for a    putative ACT domain repeat protein-   23. SEQ ID NO: 23 Sucrose-UDP glucosyltransferase 2 forward (for)    primer-   24. SEQ ID NO: 24 Sucrose-UDP glucosyltransferase 2 reverse (rev)    primer-   25. SEQ ID NO: 25 Putative Bowman-Kirk trypsin inhibitor (for)    primer-   26. SEQ ID NO: 26 Putative Bowman-Kirk trypsin inhibitor rev primer-   27. SEQ ID NO: 27 Hypothetical protein Acc. No. CF279761 (for)    primer-   28. SEQ ID NO: 28 Hypothetical protein Acc. No. CF279761 rev primer-   29. SEQ ID NO: 29 Phenylalanine ammonia-lyase (for) primer-   30. SEQ ID NO: 30 Phenylalanine ammonia-lyase rev primer-   31. SEQ ID NO: 31 Metallothioneine-like protein 1 (for) primer-   32. SEQ ID NO: 32 Metallothioneine-like protein 1 rev primer-   33. SEQ ID NO: 33 Catalase (for) primer-   34. SEQ ID NO: 34 Catalase rev primer-   35. SEQ ID NO: 35 Putative stress-related protein (for) primer-   36. SEQ ID NO: 36 Putative stress-related protein rev primer-   37. SEQ ID NO: 37 Putative translation initiation factor SUI1 (for)    primer-   38. SEQ ID NO: 38 Putative translation initiation factor SUI1 rev    primer-   39. SEQ ID NO: 39 Polyubiquitin (for) primer-   40. SEQ ID NO: 40 Polyubiquitin rev primer-   41. SEQ ID NO: 41 Glutathione S-transferase II (for) primer-   42. SEQ ID NO: 42 Glutathione S-transferase II rev primer-   43. SEQ ID NO: 43 Metallothioneine-like protein 2 (for) primer-   44. SEQ ID NO: 44 Metallothioneine-like protein 2 rev primer-   45. SEQ ID NO: 45 Translational initiation factor eIF1 (for) primer-   46. SEQ ID NO: 46 Translational initiation factor eIF1 rev primer-   47. SEQ ID NO: 47 OSJNBa0024F24.10 (unknown protein) (for) primer-   48. SEQ ID NO: 48 OSJNBa0024F24.10 (unknown protein) rev primer-   49. SEQ ID NO: 49 Protein similar to Histone 3.2-614 (for) primer-   50. SEQ ID NO: 50 Protein similar to Histone 3.2-614 rev primer-   51. SEQ ID NO: 51 OSJNBa0042L16.3 (for) primer-   52. SEQ ID NO: 52 OSJNBa0042L16.3 rev primer-   53. SEQ ID NO: 53 BPSI.1-5′ primer-   54. SEQ ID NO: 54 BPSI.1-3′ primer-   55. SEQ ID NO: 55 BPSI.2-5′ primer-   56. SEQ ID NO: 56 BPSI.2-3′ primer-   57. SEQ ID NO: 57 BPSI.3-5′ primer-   58. SEQ ID NO: 58 BPSI.3-3′ primer-   59. SEQ ID NO: 59 BPSI.4-5′ primer-   60. SEQ ID NO: 60 BPSI.4-3′ primer-   61. SEQ ID NO: 61 BPSI.5-5′ primer-   62. SEQ ID NO: 62 BPSI.5-3′ primer-   63. SEQ ID NO: 63 BPSI.6-5′ primer-   64. SEQ ID NO: 64 BPSI.6-3′ primer-   65. SEQ ID NO: 65 BPSI.7-5′ primer-   66. SEQ ID NO: 66 BPSI.7-3′ primer-   67. SEQ ID NO: 67 BPSI.8-5′ primer-   68. SEQ ID NO: 68 BPSI.8-3′ primer-   69. SEQ ID NO: 69 BPSI.9-5′ primer-   70. SEQ ID NO: 70 BPSI.9-3′ primer-   71. SEQ ID NO: 71 BPSI.10-5′ primer-   72. SEQ ID NO: 72 BPSI.10-3′ primer-   73. SEQ ID NO: 73 BPSI.11-5′ primer-   74. SEQ ID NO: 74 BPSI.11-3′ primer-   75. SEQ ID NO: 75 5′-CURAY-3′ plant branchpoint consensus sequences    1-   76. SEQ ID NO: 76 5′-YURAY-3′ plant branchpoint consensus sequences    2-   77. SEQ ID NO: 77 5′-(AG)(AG)/GT(AGT)(AGT)(GTC)-3′ preferred 5′    splice-site-   78. SEQ ID NO: 78 5′ splice site dinucleotide 5′-GT-3′-   79. SEQ ID NO: 79 3′ splice site trinucleotide 5′-CAG-3′-   80. SEQ ID NO: 80 5′ splice site plant consensus sequence    5′-AG::GTAAGT-3′-   81. SEQ ID NO: 81 3′ splice site plant consensus sequence    5′-CAG::GT-3′-   82. SEQ ID NO: 82 Sequence of the first intron isolated from the    Oryza sativa metallothioneine-like gene (accession No. AP002540)    including sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sites    of the intron sequence BPSI.1 (SEQ ID NO:1)-   83. SEQ ID NO: 83 Sequence of the first intron isolated from the O.    sativa Sucrose UDP Glucosyltransferase-2 gene (accession No.    AC084380) including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.2 (SEQ ID NO:2)-   84. SEQ ID NO: 84 Sequence of the second intron isolated from the O.    sativa Sucrose UDP Glucosyltransferase-2 gene (accession No.    AC084380) including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.3 (SEQ ID NO:3)-   85. SEQ ID NO: 85 Sequence of the third intron isolated from the O.    sativa Sucrose UDP Glucosyltransferase-2 gene (accession No.    AC084380) including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.4 (SEQ ID NO:4)-   86. SEQ ID NO: 86 Sequence of the eighth intron isolated from the    Oryza sativa gene encoding for the Sucrose transporter (GenBank    accession No. AF 280050) including sequences 5′ and 3′ adjacent to    the 5′ and 3′ splice sites of the intron sequence BPSI.5 (SEQ ID    NO:5)-   87. SEQ ID NO: 87 Sequence of the eighth intron isolated from the    Oryza sativa gene encoding for the Sucrose transporter (accession    No. AF 280050) including modified 5′ and 3′ splice sites and    sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sites of the    intron sequence BPSI.5 (SEQ ID NO:5)-   88. SEQ ID NO: 88 Sequence of the fourth intron isolated from the    Oryza sativa gene encoding for an unknown protein with homology to    the A. thaliana chromosome II sequence from clones T22013, F12K2    encoding for a putative lipase (AC006233) including sequences 5′ and    3′ adjacent to the 5′ and 3′ splice sites of the intron sequence    BPSI.6 (SEQ ID NO:6)-   89. SEQ ID NO: 89 Sequence of the fourth intron isolated from the    Oryza sativa gene encoding for an unknown protein with homology to    the A. thaliana chromosome II sequence from clones T22013, F12K2    encoding for a putative lipase (AC006233) including modified 5′ and    3′ splice sites and sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.6 (SEQ ID NO:6)-   90. SEQ ID NO: 90 Sequence of the fourth intron isolated from the    Oryza sativa gene (accession No. BAB90130) encoding for a putative    cinnamyl-alcohol dehydrogenase including sequences 5′ and 3′    adjacent to the 5′ and 3′ splice sites of the intron sequence BPSI.7    (SEQ ID NO:7)-   91. SEQ ID NO: 91 Sequence of the fourth intron isolated from the    Oryza sativa gene (accession No. BAB90130) encoding for a putative    cinnamyl-alcohol dehydrogenase including modified 5′ and 3′ splice    sites and sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sites    of the intron sequence BPSI.7 (SEQ ID NO:7)-   92. SEQ ID NO: 92 Sequence of the second intron isolated from the    Oryza sativa gene (accession No. AC084766) encoding for a putative    ribonucleoprotein including sequences 5′ and 3′ adjacent to the 5′    and 3′ splice sites of the intron sequence BPSI.8 (SEQ ID NO:8)-   93. SEQ ID NO: 93 Sequence of the second intron isolated from the    Oryza sativa gene (accession No. AC084766) encoding for a putative    ribonucleoprotein including modified 5′ and 3′ splice sites and    sequences 5′ and 3′ adjacent to the 5′ and 3′ splice sites of the    intron sequence BPSI.8 (SEQ ID NO:8)-   94. SEQ ID NO: 94 Sequence of the third intron isolated from the    Oryza sativa gene (accession No. AP003300) encoding for a putative    protein including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.10 (SEQ ID NO:10)-   95. SEQ ID NO: 95 Sequence of the third intron isolated from the    Oryza sativa gene (accession No. AP003300) encoding for a putative    protein including modified 5′ and 3′ splice sites and sequences 5′    and 3′ adjacent to the 5′ and 3′ splice sites of the intron sequence    BPSI.10 (SEQ ID NO:10)-   96. SEQ ID NO: 96 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. L37528) encoding for a MADS3 box    protein including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.11 (SEQ ID NO:11)-   97. SEQ ID NO: 97 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. L37528) encoding for a MADS3 box    protein including modified 5′ and 3′ splice sites and sequences 5′    and 3′ adjacent to the 5′ and 3′ splice sites of the intron sequence    BPSI.11 (SEQ ID NO:11)-   98. SEQ ID NO: 98 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. CB625805) encoding for a putative    Adenosylmethionine decarboxylase including sequences 5′ and 3′    adjacent to the 5′ and 3′ splice sites of the intron sequence    BPSI.12 (SEQ ID NO:12)-   99. SEQ ID NO: 99 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. CF297669) encoding for a Aspartic    proteinase including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.13 (SEQ ID NO:13)-   100. SEQ ID NO: 100 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. CB674940) encoding for a Lec14b    protein including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.14 (SEQ ID NO:14)-   101. SEQ ID NO: 101 Sequence of the first intron isolated from    the O. sativa gene (accession No. CA128696) encoding for a putative    mannose-binding rice lectin including sequences 5′ and 3′ adjacent    to the 5′ and 3′ splice sites of the intron sequence BPSI.15 (SEQ ID    NO:15)-   102. SEQ ID NO: 102 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. BX928664) encoding for a putative    Reticulon including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.16 (SEQ ID NO:16)-   103. SEQ ID NO: 103 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. AA752970) encoding for a glycolate    oxidase including sequences 5′ and 3′ adjacent to the 5′ and 3′    splice sites of the intron sequence BPSI.17 (SEQ ID NO:17)-   104. SEQ ID NO: 104 Sequence of the first intron isolated from the    Oryza sativa clone GI 34763855 including sequences 5′ and 3′    adjacent to the 5′ and 3′ splice sites of the intron sequence    BPSI.18 (SEQ ID NO:18)-   105. SEQ ID NO: 105 Sequence of the first intron isolated from the    Oryza sativa clone GI 32533738 including sequences 5′ and 3′    adjacent to the 5′ and 3′ splice sites of the intron sequence    BPSI.19 (SEQ ID NO:19)-   106. SEQ ID NO: 106 Sequence of the first intron isolated from the    Oryza sativa gene (accession No. CF279761) encoding for a    hypothetical protein including sequences 5′ and 3′ adjacent to the    5′ and 3′ splice sites of the intron sequence BPSI.20 (SEQ ID    NO:20).-   107. SEQ ID NO: 107 Sequence of the first intron isolated from    the O. sativa gene (accession No. CF326058) encoding for a putative    membrane transporter including sequences 5′ and 3′ adjacent to the    5′ and 3′ splice sites of the intron sequence BPSI.21 (SEQ ID    NO:21).-   108. SEQ ID NO: 108 Sequence of the first intron isolated from    the O. sativa gene (accession No. C26044) encoding for a putative    ACT domain repeat protein including sequences 5′ and 3′ adjacent to    the 5′ and 3′ splice sites of the intron sequence BPSI.22 (SEQ ID    NO:22).-   109. SEQ ID NO: 109 Binary vector pBPSMM291-   110. SEQ ID NO: 110 Binary vector pBPSMM305-   111. SEQ ID NO: 111 Binary vector pBPSMM350-   112. SEQ ID NO: 112 Binary vector pBPSLM139-   113. SEQ ID NO: 113 Artificial sequence: cassette from vector    pBPSMM355 (OsCP12::BPSI.1) comprising Os CP12 promoter (bp 1-854)    and BPSI.1 intron (bp 888-1470).-   114. SEQ ID NO: 114 Artificial sequence: cassette from vector    pBPSMM355 (ZmHRGP::BPSI.1) comprising Maize    [HRGP]hydroxyproline-rich glycoprotein (extensin) 5′/UTR promoter    (bp 1-1184) and oryza sativa BPSI.1 intron (bp 1217-1799)-   115. SEQ ID NO: 115 Artificial sequence: cassette from vector    pBPSMM358 (OsCCoAMT1::BPSI.1) comprising p-caffeoyl-CoA    3-O-methyltransferase [CoA-O-Methyl] promoter (bp 1-1034) and BPSI.1    intron (1119-1701)-   116. SEQ ID NO: 116 Artificial sequence: cassette from vector    EXS1025 (ZmGlobulin1::BPSI.1) comprising Maize Globulin-1 [ZmGlg1]    promoter (W64A) (bp 1-1440) and BPSI.1 intron (1443-1999)-   117. SEQ ID NO: 117 Artificial sequence: cassette from vector    pBPSMM369 (OsVATPase::BPSI.1) comprising putative Rice    H+-transporting ATP synthase 5′/UTR promoter (1-1589) and BPSI.1    intron (1616-2198)-   118. SEQ ID NO: 118 Artificial sequence: cassette from vector    pBPSMM366 (OsC8,7S1::BPSI.1) comprising Putative Rice C-8,7 Sterol    isomerase promoter (1-796) and BPSI.1 intron (827-1409)-   119. SEQ ID NO: 119 Artificial sequence: cassette from vector    pBPSMM357 (ZmLDH::BPSI.1) comprising maize gene Lactate    Dehydrogenase 5′/UTR promoter (bp 1-1062) and BPSI.1 intron (bp    1095-1677).-   120. SEQ ID NO: 120 Artificial sequence: cassette from vector    pBPSLM229 (ZmLDH::BPSI.5) comprising maize gene Lactate    Dehydrogenase 5′/UTR promoter (bp 1-1062) and BPSI.5 intron (bp    1068-1318)-   121. SEQ ID NO: 121 Artificial sequence: cassette from vector    pBPSMM371 (OsLea::BPSI.1) comprising rice Lea (Late Embryogenesis    Abundant) promoter (bp 1-1386) and BPSI.1 intron (bp 1387-2001)

EXAMPLES Chemicals

Unless indicated otherwise, chemicals and reagents in the Examples wereobtained from Sigma Chemical Company (St. Louis, Mo.), restrictionendonucleases were from New England Biolabs (Beverly, Mass.) or Roche(Indianapolis, Ind.), oligonucleotides were synthesized by MWG BiotechInc. (High Point, N.C.), and other modifying enzymes or kits regardingbiochemicals and molecular biological assays were from Clontech (PaloAlto, Calif.), Pharmacia Biotech (Piscataway, N.J.), Promega Corporation(Madison, Wis.), or Stratagene (La Jolla, Calif.). Materials for cellculture media were obtained from Gibco/BRL (Gaithersburg, Md.) or DIFCO(Detroit, Mich.). The cloning steps carried out for the purposes of thepresent invention, such as, for example, restriction cleavages, agarosegel electrophoresis, purification of DNA fragments, transfer of nucleicacids to nitrocellulose and nylon membranes, linking DNA fragments,transformation of E. coli cells, growing bacteria, multiplying phagesand sequence analysis of recombinant DNA, are carried out as describedby Sambrook (1989). The sequencing of recombinant DNA molecules iscarried out using ABI laser fluorescence DNA sequencer following themethod of Sanger (Sanger 1977).

Example 1 Identification and Characterization of IME-Introns in HighlyExpressing Genes 1.1 Identification of Strongly and ConstitutivelyExpressed Oryza sativa Gene Candidates

Using the above described “sequencing by hybridization method” in silicoclone distribution analysis of rice cDNA libraries have been performed.

The rice cDNA clone distribution profiles were derived from about 7.6million rice cDNA clones, which were generated over 23 rice cDNAlibraries of different tissues at different developmental stages andbiotic/abiotic treatments. Method for the production of cDNA librariesare well known in the art (e.g. Gubler U, and Hoffman B J. (1983) Asimple and very efficient method for generating cDNA libraries. Gene25(2-3):263-269.; Jung-Hwa Oh et al. (2003) An improved method forconstructing a full-length enriched cDNA library using small amounts oftotal RNA as a starting material. EXPERIMENTAL and MOLECULAR MEDICINE35(6):586-590; Lanfranchi et al. (1996) Identification of 4370 expressedsequence tags from a 3′-end-specific cDNA library of human skeletalmuscle by DNA sequencing and filter hybridization. Genome Res.6(1):35-42). Furthermore, a comprehensive description of cDNA libraryconstruction is provided in 1) Cowell and Austin. cDNA LibraryProtocols. In Methods in Molecular Biology, Volume 69, October 1996,Humana Press, Scientific and medical publishers, ISBN: 0-89603-383-X;and 2) Ying, Shao-Yao. Generation of cDNA Libraries, Methods andProtocols. In Methods in Molecular Biology, Volume 221, February 2003,Humana Press, Scientific and medical publishers, ISBN: 1-58829-066-2.

All of the clones were clustered into a total of 300,408 rice clustersusing the above described (see “sequencing by hybridization method”, or“HySeq-technology”) high-throughput technology of 288 plant-specific 7mer-oligonucleotide fingerprinting. For each generated cluster, cloneshave further been clustered into different variants using more stringentcutoff value of the hybridization pattern similarity, leading to 335,073rice clone variants. Therefore, within each variant for given cluster,clones are more homogeneous. The distribution of rice cDNA clones overthe 23 normalized cDNA libraries for given variants provides the ricevariant expression profiles. The normalized cDNA library was produced byfirst adjusting the orignal library clone size to the average clone sizeof all of the 23 libraries, then adjusting the number of clones pervariant in that library based on the adjusted total number of clones inthat library.

Rice clones are selected from the rice clusters for sequencing togenerate rice EST data. In using the clones distribution profiles of335,073 rice variants, 145 variants were selected based on the number ofclones exceeding top 1% of the clone distribution across the entirelibrary for over each of 23 libraries, and genes were identified usingthe homologs to the EST sequences derived from the variants. Thesecandidate genes showed strong, constitutive, and ubiquitous expression.The rice EST sequences homolog to these candidate genes were mapped tothe rice genomic DNA sequences. Top 15 candidates out of 145 wereselected based on availability of genomic sequences, annotation, andhigh level of expression (Table 2).

TABLE 2 Gene candidates for potential IME-introns Candidate geneAnnotation 1 sucrose-UDP glucosyltransferase 2 2 putative Bowman-Kirktrypsin inhibitor 3 Hypothetical Protein 4 phenylalanine ammonia-lyase 5metallothioneine-like protein1 6 Catalase 7 putative stress-relatedprotein 8 putative translation initiation factor SUI1 9 Polyubiquitin 10glutathione S-transferase II 11 metallothioneine-like protein2 12translational initiation factor eIF1 13 OSJNBa0024F24.10 (UnknownProtein) 14 Similar to Histone 3.2-614 15 OSJNBa0042L16.3

1.2 Validation of Highly Expressing Gene Candidates Using Real TimeRT-PCR

Expression levels of the endogenous genes representing these 15candidates were measured at the mRNA levels using LightCycler. Total RNAwas extracted from rice plants at various developmental stages andtissues with and without drought stress (6, 12, 24, and 48 hr bywithholding water) using Qiagen RNeasy Plant Mini Kit (Cat. No 74904).Quality and quantity of the RNA were determined using Molecular ProbesRiboGreen Kit (Cat. No. R-11490) on the Spectra MAX Gemini. One μg ofRNA was used for RT-PCR (Roche RT-PCR AMV kit, Cat. No. 1483188) in thereaction solution I (1 μg RNA, 2 μL 10× Buffer, 4 μL 25 mM MgCl₂, 2 μL 1mM dNTPs, 2 82 L 3.2 μg Random Primers, 1 μL 50 units RNase Inhibitor,0.8 μL 20 units AMV-RT polymerase, fill to 20 μL with sterile water)under the optimized PCR program (25° C. 10 min, 42° C. 1 hr, 99° C. 5min, 4° C. stop reaction).

The RT-PCR samples were used for the LightCycler reaction (11.6 μLsterile water, 2.4 μL 25 mM MgCl₂, 2 μL SYBR Green Polymerase mix, 2 μL10 mM Specific Primer Mix, 2 μL RT-PCR reaction product) under theoptimized program (95° C. 5 min, 95° C. 30 sec, 61° C. 40 sec, 72° C. 40sec and repeat steps 2-4 for 30 cycles, 72° C. 10 min, and 4° C. stopreaction) provided by Roche (LightCycler FastStart DNA Master SYBR GreenI, Cat. No. 3003230).

TABLE 3 Primer sequences of the gene candidates Gene Primers SEQ ID NO.Sucrose-UDP glucosyltransferase 2 Fwd: 5′-tttgtgcagcccgctttctacgag 23Rev: 5′-acggccaacgggacggtgcta 24 Putative Bowman-Birk trypsin inhib-Fwd: 5′-gtcctcgccggcatcgtcac 25 itor Rev: 5′-cagaacggcgggttgatcc 26Hypothetical protein Fwd: 5′-agctcgctcgcggtctt 27 Acc. No. CF279761Rev: 5′-acagggcccaagtcgtgtgc 28 Phenylalanine ammonia-lyaseFwd: 5′-aggtctcgccatcgtcaatg 29 Rev: 5′-cgagacgggcgttgt 30Methallothioneine-like protein 1 Fwd: 5′-ggctgcggaggatgcaagatg 31Rev: 5′-ggggttgcaggtgcagttgtcg 32 Catalase Fwd: 5′-ggcgtcaacacctacacctt33 Rev: 5′-tgcactgcagcatcttgtcgtc 34 Putative stress-related proteinFwd: 5′-gtggatgccacggtgcaagag 35 Rev: 5′-ggggaggtactgtgctc 36Putative translation initiation factor Fwd: 5′-tgcggaagccaatgctga 37SUI1 Rev: 5′-ccagccctgaactaggaacgtc 38 PolyubiquitinFwd: 5′-tcaggggaggcatgcaaa 39 Rev: 5′-tgcataccaccacggagacgaa 40Glutathione S-transferase II Fwd: 5′-cgatttctccaaaggcgagcac 41Rev: 5′-tgcgggtatgcgtccaaca 42 Metallothioneine-like protein 2Fwd: 5′-cagccaccaccaagaccttcg 43 Rev: 5′-ctgcagctggtgccacacttgc 44Translational initiation factor elF1 Fwd: 5′-tcccaactgccttcgatccctt 45Rev: 5′-tggacagtggtcaggctcttacgg 46 OSJNBa0024F24.10 (unknownFwd: 5′-gagttctaccagttcagcgacc 47 protein) Rev: 5′-aacccgaaggcgttgac 48Similar to Histone 3.2-614 Fwd: 5′-agaccgcccgcaagtc 49Rev: 5′-cttgggcatgatggtgacgc 50 OSJNBa0042L16.3Fwd: 5′-ccaagagggagtgctgtatgccaa 51 Rev: 5′-acgaggaccaccacggtacccat 52

Standardizing the concentration of RNA (1 μg) in each of the RT-PCRreactions was sufficient to directly compare the samples if the sameprimers were used for each Lightcycler reaction. The output results werea number that corresponds to the cycle of PCR at which the samplereaches the inflection point in the log curve generated. The lower thecycle numbers the higher the concentration of target RNA present in thesample. Each sample was repeated in triplicate and an average wasgenerated to produce the sample “crosspoint” value. The lower thecrosspoint, the stronger the target gene was expressed in that sample.(Roche Molecular Biochemicals LightCycler System: Reference Guide May1999 version) Based on the LightCycler results, 11 candidates wereselected (Table 4).

TABLE 4 LightCycler results representing expression of the rice genecandidates at the mRNA levels. Well-watered conditions Panicle Genecandidates Drought stressed rice root (R) and during [strong &constitutive shoot (S) (hr withholding water) flowering expression] R6R12 R24 R48 S6 S12 S24 S48 seedling stage shoots flowers Unknown 21.121.6 N/A 20.3 20.5 21.7 N/A 21.0 23.3 22.7 21.4 23.7 Catalase 21.2 22.726.7 26.0 21.9 21.7 N/A 27.8 22.8 31 20.6 23.5 GSTII 20.6 20.3 23.3 23.721.8 23.2 N/A 20.6 24.4 22.6 22.1 24.8 Hypothetical Protein 31 31 31 3131 31 31 31 31 31 27.4 27.0 Metallothioneine 1 20.1 21.5 16.5 16.3 18.319.8 N/A 19.2 21.0 22.5 20.6 20.6 Metallothioneine 2 20.2 20.8 23.8 24.818.5 18.7 N/A 18.7 19.9 17.8 21.2 19.2 PolyUbuiquitin 19.5 19.1 19.420.4 19.1 20.4 N/A 19.8 22.8 20.7 20.0 22.6 Stress Related 24.1 23.923.7 24.0 23.4 23.4 N/A 23.3 24.6 24.0 23.6 24.9 Protein Sucrose-UDP21.3 21.9 26.6 26.7 20.7 20.9 27.2 22.6 20.9 19.1 20.7 26.0glucoryltransferase 2 SUI1 21.3 21.1 23.1 23.6 21.9 22.8 N/A 21.7 24.423.8 22.9 30.2 TIF 23.6 23.6 N/A 22.9 22.1 23.3 N/A 23.1 24.6 23.8 22.823.7 Trypsin Inhibitor 24.0 23.8 24.5 25.0 22.8 23.3 23.5 23.2 26.2 23.823.2 23.05

The numbers represent PCR cycle that reaches the start of theexponential curve of the PCR product. Lower the number indicates thathigher the expression of the endogenous gene is.

1.3 Identification of IME-Introns

Candidate introns were isolated using the public available genomic DNAsequences (e.g. ncbi.nlm.nih.gov/genomes/PLANTS/PlantList.html), leadingto a total of 20 introns, mostly first, second, and/or third intronsfrom the targeted genes. These intron sequences were screened by thefollowing IME criteria:

-   -   5′ splice site GT, 3′ splice site CAG    -   At least 40% AT rich over 100 nucleotides downstream from the 5′        splice site GT    -   At least 50% AT rich over 100 nucleotides upstream from the 3′        splice site CAG    -   At least 55% AT rich and 35% T rich over the entire intron    -   CURAY branch point    -   Intron size less than 1 kb

Selected intron candidates can retain up to 50 by exon sequencesupstream and downstream of the 5′ and 3′ splice sites, respectively.

After screening the intron sequences against the IME criteria describedabove, four out of the 20 candidates were chosen and named as follows.

TABLE 5 The intron candidates Intron name Annotation BPSI.1 (SEQ IDNo. 1) Metallothioneine1 first intron BPSI.2 (SEQ ID No. 2) Sucrose-UDPglucosyltransferase2 first intron BPSI.3 (SEQ ID No. 3) Sucrose-UDPglucosyltransferase2 second intron BPSI.4 (SEQ ID No. 4) Sucrose-UDPglucosyltransferase2 third intron

1.4 Isolation of the Intron Candidates

Genomic DNA from rice was extracted using the Qiagen DNAeasy Plant MiniKit (Qiagen). Genomic DNA regions containing introns of interest wereisolated using conventional PCR. Approximately 0.1 μg of digestedgenomic DNA was used for the regular PCR reaction (see below). Theprimers were designed based on the rice genomic sequences. One μL of thediluted digested genomic DNA was used as the DNA template in the primaryPCR reaction. The reaction comprised six sets of primers (Table 6) in amixture containing Buffer 3 following the protocol outlined by an ExpandLong PCR kit (Cat #1681-842, Roche-Boehringer Mannheim). The isolatedDNA was employed as template DNA in a PCR amplification reaction usingthe following primers:

TABLE 6 Primer sequences Primer name Sequence BPSI.1-5′ (SEQ ID No. 53)5′-cccgggcaccctgcggagggtaagatccgatcacc BPSI.1-3′ (SEQ ID No. 54)5′-cggaccggtacatcttgcatctgcatgtac BPSI.2-5′ (SEQ ID No. 55)5′-cccgggcacccttcaccaggttcgtgctgatttag BPSI.2-3′ (SEQ ID No. 56)5′-cggaccgaaccagcctgcgcaaataacag BPSI.3-5′ (SEQ ID No. 57)5′-cccgggcacctcctgaggagtgcacaggtttg BPSI.3-3′ (SEQ ID No. 58)5′-cggaccgggagataacaatcccctcctgcatg BPSI.4-5′ (SEQ ID No. 59)5′-cccgggcacccagcttgtggaagaagggtatg BPSI.4-3′ (SEQ ID No. 60)5′-cggaccggttgttggtgctgaaatatacatc

Amplification was carried out in the PCR reaction (5 μL 10× AdvantagePCR Mix [Eppendorf], 5 μL genomic DNA [corresponds to approximately 80ng], 2.5 mM of each dATP, dCTP, dGTP and dTTP [Invitrogen: dNTP mix], 1μL of 20 μM 5′-intron specific primer 20 μM, 1 82 L of 20 μM 3′ intronspecific primer, 1 μL TripleMaster DNA Polymerase mix [Eppendorf], in afinal volume of 50 μL) under the optimized PCR program (1 cycle with 15sec at 94° C. and 1 min at 80° C. 35 cycles with 15 sec at 94° C., 1 minat 58° C. and 1 min at 72° C.) provided by Thermocycler (T3 ThermocyclerBiometra).

The PCR product was applied to an 1% (w/v) agarose gel and separated at80V. The PCR products were excised from the gel and purified with theaid of the Qiagen Gel Extraction Kit (Qiagen, Hilden, Germany). The PCRproduct can be cloned directly into vector pCR4-TOPO (Invitrogen)following the manufacturer's instructions, i.e. the PCR product obtainedwas inserted into a vector having T overhangs with its A overhangs and atopoisomerase.

1.5 Vector Construction

The base vector to which the intron candidates were clone in waspBPSMM267. This vector comprises the maize ubiquitin promoter with nointronic sequence, followed by multiple cloning sites (MCS) to be usedfor addition of introns of interest, then the GUSint ORF (including thepotato invertase [PIV]2 intron to prevent bacterial expression),followed by nopaline synthase (NOS) terminator. The intron-containingexpression vectors were generated by ligation of XmaI-RsrII digestedintron PCR products into XmaI-RsrII linearized pBPSMM267, therebyresulting in the following vectors (Table 7).

TABLE 7 GUS chimeric constructs containing introns in the 5′ UTRpUC-based Composition of the expression expression cassette(promoter::intron::reporter vector Binary vector gene::terminator)pBPSMM291 pBPSMM350 Zm.ubiquitin promoter::BPSI.1::GUS::NOS3′ pBPSMM293pBPSMM353 Zm.ubiquitin promoter::BPSI.2::GUS::NOS3′ pBPSMM294 pBPSMM312Zm.ubiquitin promoter::BPSI.3::GUS::NOS3′ pBPSMM295 pBPSMM310Zm.ubiquitin promoter::BPSI.4::GUS::NOS3′

1.6 Plant Analysis for Identifying IME-Introns

These experiments were performed by bombardment of plant tissues orculture cells (Example 4.1), or by Agrobacterium-mediated transformation(Example 4.3). The target tissues for these experiments can be planttissues (e.g. leaf or root), cultured cells (e.g. maize BMS), or planttissues (e.g. immature embryos) for Agrobacterium protocols.

1.6.1 Transient Assays

To identify IME-introns, four introns (BPSI.1, 2, 3, and 4) were testedusing Microprojectile bombardment. The maize ubiquitin promoter(Zm.ubiquitin) without any intronic sequence was used as basalexpression (negative control). Introns of interest were cloned into the5′UTR region of Zm.ubiquitin promoter. Maize ubiquitin intron was usedas a positive control to measure the relative levels of expressionenhanced by introns of interest based on GUS expression. Strongenhancement with BPSI.1 and BPSI.2 introns was detected (Table 8).BPSI.3 intron showed medium enhancement levels of GUS expression. Noexpression was detected with BPSI.4 intron.

TABLE 8 Transient GUS expression testing for intron-mediated enhancementIntron candidates GUS expression* Zm.ubiquitin promoter alone (negativecontrol) ++   50%** Zm.ubiquitin promoter + Zm.ubiquitin intron1 ++++100% (positive control) Zm.ubiquitin promoter + BPSI.1 (pBPSMM291) ++++100% Zm.ubiquitin promoter + BPSI.2 (pBPSMM293) ++++ 100% Zm.ubiquitinpromoter + BPSI.3 (pBPSMM294) +++  80% Zm.ubiquitin promoter + BPSI.4(pBPSMM295) −  0% *GUS histochemical assays: a range of GUS activities(− no expression to ++++ high expression), **Relative GUS expressioncompared to the expression controlled by maize ubiquitin promoter fusedwith Zm.ubiquitin intron.

1.6.2 Analysis of IME-Intron Candidates in Stably Transformed Maize

The binary vectors pBPSMM350, pBPSMM353, pBPSMM312, and pBPSMM310 (Table7), were transformed into maize using Agrobacterium-mediatedtransformation (Example 4.3). The levels and patterns of GUS expressioncontrolled by BPSI.1, BPSI.2, BPSI.3, or BPSI.4 intron were comparedwith those controlled by Zm.ubiquitin intron. BPSI.1, BPSI.2 and BPSI.3introns enhanced expression in roots, leaves, and kernels throughout thevarious development stages at a similar level to that observed intransient assays (Table 9). Expression of Zm.ubiquitin promoter withoutintron was undetectable in roots and leaves and was limited in kernelsto the endosperm. Expression of Zm.ubiqutin promoter with BPSI.4 intronexhibited the same expression patterns as those controlled byZm.ubiquitin promoter without intron. This result indicates that atransient assay can be used as a model system and is therefore one ofthe important screening systems to identify introns that function inintron-mediated enhancement (IME) in stable transformed plants. However,the results obtained with the transient assays should be validated bythe production of stable transformed transgenic plants.

TABLE 9 GUS expression in transgenic maize plants ZmubiquitinZmubiquitin Develop- promoter:: Zmubiquitin promoter:: mentalZmubiquitin promoter:: BPSI.1 stage Organs intron no intron (pPSMM350)Five leaf Roots ++++ − ++++ Leaves ++++ − +++ Flowering Leaves ++++ −+++ Late Kernels ++++ ++** +++ reproductive Zmubiquitin ZmubiquitinZmubiquitin Develop- promoter:: promoter:: promoter:: mental BPSI.2BPSI.3 BPSI.4 stage Organs (pBPSMM353) (pBPSMM312) (pBPSMM310) Five leafRoots +++ +++ − Leaves +++ ++ − Flowering Leaves +++ +++ − Late Kernels+++ +++ ++** reproductive *GUS histochemical assays: a range of GUSactivities (− no expression to ++++ high expression), **only inendosperm, ND: not determined

Example 2 IME-Introns Located in the Annotated DNA Sequences 2.1 InSilico Screening System

The in silico intron-screening system for identifying introns that havethe functional IME comprises three major components: (1) Generate intronsequence database and screen for intron candidates using the functionalIME criteria (indicated in Example 1.3); (2) Define the expressionprofiles of these candidate genes from which introns were selected; (3)Further examine the selected gene structures by conducting a mapping ofEST sequences onto the genomic region where the candidate genes resided.

More than 30,000 annotated rice and maize genomic sequences weredownloaded from NCBI. Intron, 5′- and 3′-UTR, promoter and terminatorsequences were isolated (in silico) from those annotated genes and theircorresponding sequence databases were generated (Table 10, 11). From thegenerated intron sequence database, more than 111,800 introns (i.e.,106049 rice introns, 4587 maize introns) were screened for potentialintron regulatory enhancement elements based on the functional IMEcriteria (see 1.3). A total of 108 potential intron candidates have beenidentified, and the protein sequences of the intron candidate genes wereretrieved from NCBI. The rice (we do not disclose maize sequences)homolog EST sequences were identified from the cDNA libraries describedin example 1 using the BLASTx algorithm (this program compares thesix-frame conceptual translation products of a nucleotide query sequence(both strands) against protein sequences) at an E-value of 1.0e⁻²⁰against those protein sequences. Using the rice variant expressionprofiling data (see example 1), the introns whose genes were homolog tothe rice genes with desirable expression profiling, such as constitutiveand tissue specific expression pattern, were selected as final in silicoidentified intron candidates for lab experimental test.

The rice UniGenes, which was derived from the EST sequence assembly,were updated using the combined public rice EST data and the EST dataobtained using the databases described in example 1, and the UniGeneexpression profiling data was generated using the rice variantexpression profiling data over the 23 different libraries described inexample 1. The newly updated rice UniGene expression profiling data wereused to help select the final 108-intron candidates. Perl scripts havebeen written to isolate intron, 5′- and 3′-UTR, terminator, and promotersequences from the entire NCBI rice and maize annotated gnomic DNAsequences for creating corresponding sequence databases, to screen forfunctional IME, and to compare the expression profiling data (seeexample 5). The introns were retrieved from the CDS (coding sequences)features of the annotated genes. A total of 106,049 rice introns and4,587 maize introns have been retrieved (Table 10) from more that 30,000annotated genes as the data summarized in Table 11 and 12.

TABLE 10 Rice/maize sequence database summary Rice Maize Intron 1060494587 5′ UTR 129 236 3′ UTR 142 694 Terminator 7 5 Promoter 69 239

TABLE 11 Rice and maize gene summary* Average Rice Maize gene length2471  3223 intron length 399 279 extron length 309 388 intron/gene   3.9 2.61 extron/gene  4 2.45 GC/intron   39% 40.8% GC/extron   54.8%55.3% *Intron or extron without gene names were excluded from thecalculation.

TABLE 12 Total number of genes in the database Species Gene Name GeneIdentifier Rice 30059 30249 Maize 1281 3549

Furthermore, The full length coding sequences of all 108 candidategenes, in which introns were isolated, were downloaded from NCBI andblasted against the Hyseq rice and maize UniGenes to identify Hyseq riceand maize homolog sequences, using BLASTN and 1.0e⁻²⁰ cutoff E-value.Top hits of rice UniGenes were selected, and the gene expressionprofiling data was examined. The EST sequences, identified as homolog tothe coding sequences of selected intron candidate genes, were retrievedand mapped along with the intron candidate gene sequences to the ricegenomic regions. Based on the UniGene expression profiling data and thecandidate gene structures, annotated and confirmed by the EST sequencealignments, nine introns were finally selected from a total of 108intron candidates and are subject to the real time RT-PCR expressiontest. Among the nine introns, four showed a constitutive expressionpattern, three preferably expressed in the early seed-developed stage,one preferably expressed in root, and one was induced in the droughtcondition (Table 13).

TABLE 13 Intron candidates selected based on the second in silicoscreening system Rice GI Intron number Sequence homology BPSI.5 (SEQ IDNo. 5) 9624451 Sucrose transporter BPSI.6 (SEQ ID No. 6) 7523493 Similarto Arabidopsis thaliana chromosome II sequence from clones T22O13,F12K2; putative lipase (AC006233) BPSI.7 (SEQ ID No. 7) 20161203putative cinnamyl-alcohol dehydrogenase BPSI.8 (SEQ ID No. 8) 18921322Putative ribonucleoprotein BPSI.9 (SEQ ID No. 9) 12061241 putativemitochondrial carrier protein BPSI.10 (SEQ ID No. 10) 20160990 Putativeprotein kinase BPSI.11 (SEQ ID No. 11) 886404 5′UTR intron (1^(st))MADS3 box protein

2.2 Isolation of the Intron Candidates

Genomic DNA from rice was extracted using the Qiagen DNAeasy Plant MiniKit (Qiagen). Genonic DNA regions containing introns of interest wereisolated using conventional PCR. Approximately 0.1 μg of digestedgenomic DNA was used for the regular PCR reaction (see below). Theprimers were designed based on the rice genomic sequences. Five μL ofthe diluted digested genomic DNA was used as the DNA template in the PCRreaction. PCR was performed using the TripleMaster PCR System(Eppendorf, Hamburg, Germany) as described by the manufacturer.

TABLE 14Primers used for amplification of widely expressed intron candidatesPrimers Sequence BPSI.5-5′ (SEQ ID No. 61)5′-cggggtaccgagctctctggtggctgaggtaagttctgttattacc BPSI.5-3′(SEQ ID No. 62) 5′-cggggatccggacaggaaaacctgaaaacaggg BPSI.6-5′(SEQ ID No. 63) 5′-cggggtaccgagctcgacgatttaggtaagtcattattgtctc BPSI.6-3′(SEQ ID No. 64) 5′-cggggatcctcactgaaacctgcagtgtagg BPSI.7-5′(SEQ ID No. 65) 5′-cggggtaccgagctcgatcctaaggtaagcactctagctg BPSI.7-3′(SEQ ID No. 66) 5′-cggggatccgtaactcaacctgtttttttta BPSI.8-5′(SEQ ID No. 67) 5′-cggggtaccgagctccaatggctaggtaagtatatgcttcc BPSI.8-3′(SEQ ID No. 68) 5′-cggggatcccccatcaagtacctgttttaag BPSI.9-5′(SEQ ID No. 69) 5′-cggggtaccgagctcgaatacctaggtaagtccatctc BPSI.9-3′(SEQ ID No. 70) 5′-cggggatcccacacaagcgacctggaaaaataagc BPSI.10-5′(SEQ ID No. 71) 5′-cggggtaccgagctcccatctttttaggtaagtatctttgcg BPSI.10-3′(SEQ ID No. 72) 5′-cggggatccggtaaagaacctgtttaatac BPSI.11-5′(SEQ ID No. 73) 5′-cggggtaccgagctctgaacaggaaggtaagttctggctttcttgcBPSI.11-3′ (SEQ ID No. 74) 5′-cggggatcctcagatcgacctggacacaaacgc

Amplification was carried out in the PCR reaction (5 μL 10× AdvantagePCR Mix [Eppendorf], 5 μL genomic DNA [corresponds to approximately 80ng], 2.5 mM of each dATP, dCTP, dGTP and dTTP [Invitrogen: dNTP mix], 1μL of 20 μM 5′-intron specific primer 20 μM, 1 μL of 20 μM 3′ intronspecific primer, 1 μL TripleMaster DNA Polymerase mix [Eppendorf], in afinal volume of 50 μL) under the optimized PCR program (1 cycle with 15sec at 94° C. and 1 min at 80° C. 35 cycles with 15 sec at 94° C., 1 minat 58° C. and 1 min at 72° C.) provided by Thermocycler (T3 ThermocyclerBiometra).

A QIAspin column was used to purify the PCR products as directed by themanufacturer (Qiagen, Valencia, Calif.), and the amplified introns wereused directly for cloning into expression vectors, as described below.

2.3 Vector Construction

The base expression vector for these experiments was pBPSMM305, whichcomprises the maize lactate dehydrogenase (LDH) promoter without introndriving expression of the GUSint gene followed by the NOS terminator.The LDH promoter has been demonstrated to direct undetectable levels ofGUS expression by colorimetric staining in the absence of an introncapable of providing IME.

Intron PCR products were digested with SacI & BamHI and cloned intopBPSMM305 linearized with SacI & BamHI, generating the followingLDH:intron:GUS expression vectors.

TABLE 15 GUS chimeric constructs containing introns in the 5′ UTRpUC-based expression Composition of the expression cassette vector(promoter::intron::reporter gene::terminator) pBPSJB041 (pBPSLI017)ZmLDH promoter::BPSI.5::GUS::NOS3′ pBPSJB042 (pBPSLI018) ZmLDHpromoter::BPSI.6::GUS::NOS3′ pBPSJB043 (pBPSLI019) ZmLDHpromoter::BPSI.7::GUS::NOS3′ pBPSJB044 (pBPSLI020) ZmLDHpromoter::BPSI.8::GUS::NOS3′ pBPSJB045 (pBPSLI021) ZmLDHpromoter::BPSI.9::GUS::NOS3′ pBPSJB046 (pBPSLI022) ZmLDHpromoter::BPSI.10::GUS::NOS3′ pBPSJB050 (pBPSLI023) ZmLDHpromoter::BPSI.11::GUS::NOS3′

Binary vector pBPSLI017 comprises the expression cassette containing theBPSI.5 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB041 into pBPSLM139 linearized with PmeI and PacI.

Binary vector pBPSLI018 comprises the expression cassette containing theBPSI.6 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB042 into pBPSLM139 linearized with PmeI and PacI.

Binary vector pBPSLI019 comprises the expression cassette containing theBPSI.7 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB043 into pBPSLM139 linearized with PmeI and PacI.

Binary vector pBPSLI020 comprises the expression cassette containing theBPSI.8 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB044 into pBPSLM139 linearized with PmeI and PacI.

Binary vector pBPSLI021 comprises the expression cassette containing theBPSI.9 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB045 into pBPSLM139 linearized with PmeI and PacI.

Binary vector pBPSLI022 comprises the expression cassette containing theBPSI.10 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB046 into pBPSLM139 linearized with PmeI and PacI.

Binary vector pBPSLI023 comprises the expression cassette containing theBPSI.11 intron and was generated by ligating in the PmeI-PacI fragmentfrom pBPSJB050 into pBPSLM139 linearized with PmeI and PacI.

2.4 Transient Assays for Identifying the Intron Functioning IME

These experiments were performed by bombardment of plant tissues orculture cells (Example 4.1), or by Agrobacterium-mediated transformation(Example 4.3). The target tissues for these experiments can be planttissues (e.g. leaf or root), cultured cells (e.g. maize BMS), or planttissues (e.g. immature embryos) for Agrobacterium protocols.

Characterization of these introns for their ability to direct IME inconjunction with the LDH promoter was undertaken via transientexpression by bombardment of expression vectors into maize leaf tissueand liquid-cultured BMS cells, respectively.

The maize lactate dehydrogenase promoter (ZmLDH) without any intronicsequence was used as basal expression (negative control). Introns ofinterest were cloned into the 5′UTR region of ZmLDH promoter. Maizeubiquitin intron was used as a positive control to measure the relativelevels of expression enhanced by introns of interest based on GUSexpression.

Due to the very low background (no detectable GUS expression) of theZmLDH promoter in the absence of intron, the presence of any GUSstaining indicates that a particular intron is capable of providing IME.Of the introns tested, BPSI.10 and BPSI.11 introns consistently yieldedthe highest GUS expression, at a level comparable to theLDH::Zm.ubiquitin intron construct. In addition to these introns,BPSI.5, BPSI.6, and BPSI.7 introns consistently resulted in anintermediate level of GUS expression in between LDH alone andLDH::Zm.ubiquitin intron. Comparable results were obtained in maizeleaves and BMS cells, indicating that the tested introns confer IME ingreen and non-green tissues (Table 16).

TABLE 16 Transient GUS expression testing for intron-mediatedenhancement GUS expression* Intron candidates leaves BMS No intron(Zm.LDH promoter alone) − − Zm.LDH + Zm.ubiquitin intron ++++ ++++(positive control) Zm.LDH promoter + BPSI.5 ++ ++ Zm.LDH promoter +BPSI.6 +++ +++ Zm.LDH promoter + BPSI.7 +++ +++ Zm.LDH promoter + BPSI.8− + Zm.LDH promoter + BPSI.9 − − Zm.LDH promoter + BPSI.10 ++++ +++Zm.LDH promoter + BPSI.11 ++++ ND *GUS histochemical assays: a range ofGUS activities (− no expression to ++++ high expression), ND: notdetermined.

Example 3 Identification of IME-Introns Located in the 5′ UntranslatedRegion 3.1 In Silico Screening System

The in silico intron screening system for identifying introns that havethe functional IME located in the ‘5 UTR comprises three majorcomponents: (1) Genome mapping of the entire rice CDS, released fromInstitute of Genome Research on Oct. 2, 2003 and the EST sequencecollections; (2) identification and selection of the introns located inthe 5′UTR using both the functional IME criteria and the rice cDNA clonedistribution profiles; (3) validation of the selected 5′UTR introns byexamining the sequence alignments among the genomic DNA, CDS and ESTs,the gene model, sequence reading frame and intron splicing sites

A total of 56,056 annotated rice CDS were mapped onto the Japonica ricegenome in which both rice CDS and genomic DNA sequences were obtainedfrom The Institute of Genome Research. Additional 422,882 rice ESTsequences of public and in-house sources were also mapped onto the ricegenome. A splicing alignment software, GeneSeqer (version Sep. 2, 2003from Iowa State University Research foundation), was used to conduct theentire genome mapping. Since both EST and CDS were mapped onto theircorresponding genomic regions, the sequence alignment coordinators[coordinators are the start and/or end positions of the genomicsequences where CDS/EST sequences aligned to] derived from the CDSmapping and the EST mapping on the same genomic region provideopportunity to identify the alignment extension of the EST sequencesalong the genomic DNA beyond the start codon of the CDS. Such sequencealignment extension from the EST sequences beyond CDS indicates theidentification of the 5′ UTRs, which have not been contained in the CDS,but in the EST sequences. The system selects these EST sequences, whichextend the sequence alignment beyong the CDS along the gnome for up to5k base long for 5′URT intron screening. For any predicted exons, thelast exon in the prediceted 5′UTR region must aligned at the sameposition of the 1^(st) exon of the CDS. The gnome mapping results haveidentified 461 genes that have their 5′ UTR containing at least oneintron.

Further stringent screen criteria that required at least 3 EST sequencesconfirming the same predicted 5′UTR introns were used to select the genecandidates, leading to identify 87 gene candidates. Those identified ESTsequences, which were considered as the same transcript as the rice CDS,were used to retrieve the rice cDNA clone distribution data or themicroarray expression data in which either the clones of thoseidentified EST sequences have been spotted on the rice microarray chipor homolog to those identified EST sequences were identified on thechip. For given the rice cDNA clone distribution profile, a gene, whichhas a cluster/variant size of more than 100 clones distributed over 23cDNA libraries, was considered highly expressed. For given themicroarray expression, a gene, which has hybridization signal intensityexceeding the top 25% percentile within the same sample, was alsoconsidered highly expressed.

In addition to the gene expression criteria used for gene candidateselection, the IME criteria (indicated in Example 1.3) were applied.

Furthermore, a validation of the selected candidate genes was conductedby examining the coincidence of the sequence alignments between EST, CDSsequences and genomic DNA sequence. Clearly the EST sequences needed tosupport the gene model predicted from the CDS. Any conflict of thesequence alignments between EST and CDS would result in the deselectingthe candidate genes. Using those criteria, a final list of 11 intronswas selected (Table 17).

TABLE 17 Intron candidates selected based on the third in silicoscreening system Rice GI Intron number Sequence homology BPSI.12 (SEQ IDNo. 12) 29620794 Putative adenosylmethionine decarboxylase BPSI.13 (SEQID No. 13) 33666702 Aspartic proteinase BPSI.14 (SEQ ID No. 14) 29678665Lec14b protein BPSI.15 (SEQ ID No. 15) 35009827 Putative mannose-bindingrice lectin BPSI.16 (SEQ ID No. 16) 41883853 Putative reticulon BPSI.17(SEQ ID No. 17) 2799981 Glycolate oxidase BPSI.18 (SEQ ID No. 18)34763855 Similar to AT4g33690/ T16L1_180 BPSI.19 (SEQ ID No. 19)32533738 N/A BPSI.20 (SEQ ID No. 20) 33657147 Hypothetical proteinBPSI.21 (SEQ ID No. 21) 33800379 Putative membrane transporter BPSI.22(SEQ ID No. 22) 2309889 Putative ACT domain repeat protein

3.2 Isolation of Introns

Genomic DNA containing introns of interest is isolated usingconventional PCR amplification with sequence specific primers (see 1.4)followed by cloning into a PCR cloning vector in the art.

3.3 Vector Construction

Introns are PCR amplified from rice genomic DNA using primers thatengineer a SacI site on the 5′ end of the intron and a BamHI site on the3′ end of the sequence. The PCR products are digested with SacI andBamHI and ligated into pBPSMM305 linearized with SacI and BamHI togenerate pUC-based expression vectors comprising the Zm.LDHpromoter::Intron candidate::GUSint::NOS terminator.

Binary vectors for stable maize transformation are constructed bydigesting the pUC expression vectors with PmeI and PacI and ligatinginto pBPSLM139 digested with PmeI and PacI.

3.4 Transient Assays for Identifying IME-Introns

These experiments are performed by bombardment of plant tissues orculture cells (Example 4.1), or by Agrobacterium-mediated transformation(Example 4.3). The target tissues for these experiments can be planttissues (e.g. leaf or root), cultured cells (e.g. maize BMS), or planttissues (e.g. immature embryos) for Agrobacterium protocols.

Example 4 Assays for Identifying IME-Introns

These experiments are performed by bombardment of plant tissues orculture cells (Example 4.1), by PEG-mediated (or similar methodology)introduction of DNA to plant protoplasts (Example 4.2), or byAgrobacterium-mediated transformation (Example 4.3). The target tissuefor these experiments can be plant tissues (e.g. leaf tissue), culturedplant cells (e.g. maize Black Mexican Sweetcorn (BMS), or plant embryosfor Agrobacterium protocols.

4.1 Transient Assay Using Microprojectile Bombardment

The plasmid constructs are isolated using Qiagen plasmid kit(cat#12143). DNA is precipitated onto 0.6 μM gold particles (Bio-Radcat#165-2262) according to the protocol described by Sanford et al.(1993) and accelerated onto target tissues (e.g. two week old maizeleaves, BMS cultured cells, etc.) using a PDS-1000/He system device(BioRad). All DNA precipitation and bombardment steps are performedunder sterile conditions at room temperature.

Black Mexican Sweet corn (BMS) suspension cultured cells are propagatedin BMS cell culture liquid medium [Murashige and Skoog (MS) salts (4.3g/L), 3% (w/v) sucrose, myo-inositol (100 mg/L), 3 mg/L2,4-dichlorophenoxyacetic acid (2,4-D), casein hydrolysate (1 g/L),thiamine (10 mg/L) and L-proline (1.15 g/L), pH 5.8]. Every week 10 mLof a culture of stationary cells are transferred to 40 mL of freshmedium and cultured on a rotary shaker operated at 110 rpm at 27° C. ina 250 mL flask.

60 mg of gold particles in a siliconized Eppendorf tube are resuspendedin 100% ethanol followed by centrifugation in a Mini centrifuge C1200(National Labnet Co. Woodbridge, N.J.) for 30 seconds. The pellet isrinsed once in 100% ethanol and twice in sterile water withcentrifugation after each wash. The pellet is finally resuspended in 1mL sterile 50% glycerol. The gold suspension is then divided into 50 μLaliquots and stored at 4° C. The following reagents are added to onealiquot: 5 μL of 1 μg/μL total DNA, 50 μL 2.5M CaCl₂, 20 μL 0.1Mspermidine, free base. The DNA solution is vortexed for 1 minute andplaced at −80° C. for 3 min followed by centrifugation for 10 seconds ina Mini centrifuge C1200. The supernatant is removed. The pellet iscarefully resuspended in 1 mL 100% ethanol by flicking the tube followedby centrifugation for 10 seconds. The supernatant is removed and thepellet is carefully resuspended in 50 μL of 100% ethanol and placed at−80° C. until used (30 min to 4 hr prior to bombardment). If goldaggregates are visible in the solution the tubes are sonicated for onesecond in a waterbath sonicator just prior to use.

For bombardment, two-week-old maize leaves are cut into piecesapproximately 1 cm in length and placed ad-axial side up on osmoticinduction medium M-N6-702 [N6 salts (3.96 g/L), 3% (w/v) sucrose, 1.5mg/L 2,4-dichlorophenoxyacetic acid (2,4-D), casein hydrolysate (100mg/L), and L-proline (2.9 g/L), MS vitamin stock solution (1 mL/L), 0.2M mannitol, 0.2 M sorbitol, pH 5.8]. The pieces are incubated for 1-2hours.

In the case of BMS cultured cells, one-week-old suspension cells arepelleted at 1000 g in a Beckman/Coulter Avanti J25 centrifuge and thesupernatant is discarded. Cells are placed onto round ash-free No 42Whatman filters as a 1/16 inch thick layer using a spatula. The filterpapers holding the plant materials are placed on osmotic induction mediaat 27° C. in darkness for 1-2 hours prior to bombardment. Just beforebombardment the filters are removed from the medium and placed onto on astack of sterile filter paper to allow the calli surface to partiallydry.

Each plate is shot with 6 μL of gold-DNA solution twice, at 1,800 psifor the leaf materials and at 1,100 psi for the BMS cultured cells. Tokeep the position of plant materials, a sterilized wire mesh screen islaid on top of the sample. Following bombardment, the filters holdingthe samples are transferred onto M-N6-702 medium lacking mannitol andsorbitol and incubated for 2 days in darkness at 27° C. prior totransient assays. Transient expression levels of the reporter genes aredetermined by GUS staining, quantification of luminescence or RT-PCRusing the protocols in the art. GUS staining is done by incubating theplant materials in GUS solution [100 mM NaHPO4, 10 mM EDTA, 0.05% TritonX100, 0.025% X-Gluc solution(5-bromo-4-chloro-3-indolyl-beta-D-glucuronic acid dissolved in DMSO),10% methanol, pH 7.0] at 37° C. for 16-24 hours. Plant tissues arevacuum-infiltrated 2 times for 15 minutes to aid even staining.

Transient expression levels of the reporter genes are determined bystaining, enzyme assays or RT-PCR using the protocols in the art.

4.2 Transient Assay Using Protoplasts

Isolation of protoplasts is conducted by following the protocoldeveloped by Sheen (1990). Maize seedlings are kept in the dark at 25°C. for 10 days and illuminated for 20 hours before protoplastpreparation. The middle part of the leaves are cut to 0.5 mm strips(about 6 cm in length) and incubated in an enzyme solution containing 1%(w/v) cellulose RS, 0.1% (w/v) macerozyme R10 (both from Yakult Honsha,Nishinomiya, Japan), 0.6 M mannitol, 10 mM Mes (pH 5.7), 1 mM CaCl₂, 1mM MgCl₂, 10 mM β-mercaptoethanol, and 0.1% BSA (w/v) for 3 hr at 23° C.followed by gentle shaking at 80 rpm for 10 min to release protoplasts.Protoplasts are collected by centrifugation at 100×g for 2 min, washedonce in cold 0.6 M mannitol solution, centrifuged, and resuspended incold 0.6 M mannitol (2×10⁶/m L).

A total of 50 μg plasmid DNA in a total volume of 100 μL sterile wateris added into 0.5 mL of a suspension of maize protoplasts (1×10⁶cells/mL) and mix gently. 0.5 mL PEG solution (40% PEG 4,000, 100 mMCaNO₃, 0.5 mannitol) is added and prewarmed at 70° C. with gentleshaking followed by addition of 4.5 mL MM solution (0.6 M mannitol, 15mM MgCl₂, and 0.1% MES). This mixture is incubated for 15 minutes atroom temperature. The protoplasts are washed twice by pelleting at 600rpm for 5 min and resuspending in 1.0 mL of MMB solution [0.6 Mmannitol, 4 mM Mes (pH 5.7), and brome mosaic virus (BMV) salts(optional)] and incubated in the dark at 25° C. for 48 hr. After thefinal wash step, collect the protoplasts in 3 mL MMB medium, andincubate in the dark at 25° C. for 48 hr. Transient expression levels ofthe reporter gene are determined quantification of expression ofreporter genes or RT-PCR using the protocols in the art in order todetermine potentially intron candidates that function in intron-mediatedenhancement.

4.3 Agrobacterium-Mediated Transformation in Dicotyledonous andMonocotyledonous Plants 4.3.1 Transformation and Regeneration ofTransgenic Arabidopsis thaliana (Columbia) Plants

To generate transgenic Arabidopsis plants, Agrobacterium tumefaciens(strain C58C1 pGV2260) is transformed with the various vector constructsdescribed above. The Agrobacterial strains are subsequently used togenerate transgenic plants. To this end, a single transformedAgrobacterium colony is incubated overnight at 28° C. in a 4 mL culture(medium: YEB medium with 50 μg/mL kanamycin and 25 μg/mL rifampicin).This culture is subsequently used to inoculate a 400 mL culture in thesame medium, and this is incubated overnight (28° C., 220 rpm) and spundown (GSA rotor, 8,000 rpm, 20 min). The pellet is resuspended ininfiltration medium (1/2 MS medium; 0.5 g/L MES, pH 5.8; 50 g/Lsucrose). The suspension is introduced into a plant box (Duchefa), and100 ml of SILWET L-77 (heptamethyltrisiloxan modified with polyalkyleneoxide; Osi Specialties Inc., Cat. P030196) is added to a finalconcentration of 0.02%. In a desiccator, the plant box with 8 to 12plants is exposed to a vacuum for 10 to 15 minutes, followed byspontaneous aeration. This is repeated twice or 3 times. Thereupon, allplants are planted into flowerpots with moist soil and grown underlong-day conditions (daytime temperature 22 to 24° C., nighttimetemperature 19° C.; relative atmospheric humidity 65%). The seeds areharvested after 6 weeks.

As an alternative, transgenic Arabidopsis plants can be obtained by roottransformation. White root shoots of plants with a maximum age of 8weeks are used. To this end, plants that are kept under sterileconditions in 1 MS medium (1% sucrose; 100 mg/L inositol; 1.0 mg/Lthiamine; 0.5 mg/L pyridoxine; 0.5 mg/L nicotinic acid; 0.5 g MES, pH5.7; 0.8% agar) are used. Roots are grown on callus-inducing medium for3 days (1× Gamborg's B5 medium; 2% glucose; 0.5 g/L mercaptoethanol;0.8% agar; 0.5 mg/L 2,4-D (2,4-dichlorophenoxyacetic acid); 0.05 mg/Lkinetin). Root sections 0.5 cm in length are transferred into 10 to 20mL of liquid callus-inducing medium (composition as described above, butwithout agar supplementation), inoculated with 1 mL of theabove-described overnight Agrobacterium culture (grown at 28° C., 200rpm in LB) and shaken for 2 minutes. After excess medium has beenallowed to run off, the root explants are transferred to callus-inducingmedium with agar, subsequently to callus-inducing liquid medium withoutagar (with 500 mg/L betabactyl, SmithKline Beecham Pharma GmbH, Munich),incubated with shaking and finally transferred to shoot-inducing medium(5 mg/L 2-isopentenyladenine phosphate; 0.15 mg/L indole-3-acetic acid;50 mg/L kanamycin; 500 mg/L betabactyl). After 5 weeks, and after 1 or 2medium changes, the small green shoots are transferred to germinationmedium (1 MS medium; 1% sucrose; 100 mg/L inositol; 1.0 mg/L thiamine;0.5 mg/L pyridoxine; 0.5 mg/L nicotinic acid; 0.5 g MES, pH 5.7; 0.8%agar) and regenerated into plants.

4.3.2 Transformation and Regeneration of Crop Plants

The Agrobacterium-mediated plant transformation using standardtransformation and regeneration techniques may also be carried out forthe purposes of transforming crop plants (Gelvin& Schilperoort (1995)Plant Molecular Biology Manual, 2^(nd) Edition, Dordrecht: KluwerAcademic Publ. ISBN 0-7923-2731-4; Glick & Thompson (1993) Methods inPlant Molecular Biology and Biotechnology, Boca Raton: CRC Press, ISBN0-8493-5164-2). For example, oilseed rape can be transformed bycotyledon or hypocotyl transformation (Moloney (1989) Plant Cell Reports8: 238-242). The use of antibiotics for the selection of agrobacteriaand plants depends on the binary vector and the Agrobacterium strainused for the transformation. The selection of oilseed rape is generallycarried out using kanamycin as selectable plant marker. TheAgrobacterium-mediated gene transfer in linseed (Linum usitatissimum)can be carried out using for example a technique described by Mlynarova(1994) Plant Cell Report 13:282-285. The transformation of soybean canbe carried out using, for example, a technique described in EP A1 0 424047 or in EP A1 0 397 687, U.S. Pat. No. 5,376,543, U.S. Pat. No.5,169,770. The transformation of maize or other monocotyledonous plantscan be carried out using, for example, a technique described in U.S.Pat. No. 5,591,616. The transformation of plants using particlebombardment, polyethylene glycol-mediated DNA uptake or via the siliconcarbonate fiber technique is described, for example, by Freeling &Walbot (1993) “The maize handbook” ISBN 3-540-97826-7, Springer VerlagNew York).

Example 5 Computer Algorithm for Retrieving Sequence Information fromNCBI Genebank File

The target feature keys are intron, terminator, promoter, UTR. Thefollowing script (written in computer language Pearl) is giving anexample for a computer algorithm of the invention suitable to identifysuitable intron sequences based of database information (see also FIG. 5a-f):

Example 6 Expression of Tissue-Specific Promoters in Combination withIME-Introns

BPSI.1 and BPSI.5 have been fused with various monocot promoters anddemonstrated that most of these promoters without IME-intron did notshow GUS expression, but IME-introns have enhanced expression.

6.1 Os.CP12 Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM355)

pBPSMM355 shows strong leaf-specific expression. This expression wasdetected in all tested developmental stages. No expression was detectedin any other tissue tested.

6.2 Zm.HRGP Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM370)

pBPSMM370 is strongly expressed in roots. Significant expression wasalso detected in silk and in the outermost layers of the kernel thatinclude the aleuron layer and seed coat. This expression was strongestaround the base of the kernel. Staining in silk was strongest in theregion close to the attachment point with the kernel and was detected atvery early developmental stages.

6.3 Os.CCoAMT1 Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM358)

Os.Caffeoyl-CoA-O-methyltransferase (CCoAMT1) promoter in combinationwith BPSI.1 (pBPSMM358) showed embryo-specific expression in T1 and T2kernels. The expression level was low but very specific. No expressionwas detected in any other tissue tested.

6.4 Zm.Globulin1 Promoter::BPSI.1 Intron::GUS::NOS Terminator (EXS1025)

EXS1025 is strongly expressed in the embryo. This expression startsbetween 5 days after pollination (DAP) and 10 DAP. Expression isstrongest in the scutellum and weaker in the embryo axis (plumule withleaves and internodes, primary root).

Significant expression was also detected in the outermost layers of thekernel that include the aleuron layer. Expression is strongest at stages15 DAP to 25 DAP and weaker at 30 DAP. Weak expression was sometimesdetected in the endosperm. No expression could be detected in any otherorgan including pollen.

6.5 Os.V-ATPase Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM369)

pBPSMM369 is strongly expressed in roots. This expression was detectedin all tested stages. Significant expression was also detected in allparts of the kernels and in pollen. Weak expression was detected in theleaves at early developmental stages and at flowering. This expressionwas variable in strength and was in several plants at the detectionlimit. In general, expression was higher in homozygous T1 plants than inthe heterozygous T0.

6.6 Zm.LDH Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM357)

pBPSMM357 shows weak activity in kernels. Expression in kernels wasmainly located in and around the embryo. Very weak expression was alsodetected in roots.

6.7 Os.C8,7S1 Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM366)

Os.C-8,7-sterol-isomerase promoter containing BPSI.1 (pBPSMM366) showsweak activity in roots and good expression in kernels.

6.8 Os.Lea Promoter::BPSI.1 Intron::GUS::NOS Terminator (pBPSMM371)

Os.Lea promoter in combination with BPSI.1 (pBPSMM371) showed strongembryo-specific expression in kernels. Some expression could be detectedin root tips but no expression was detected in any other tissue tested.

6.9 Zm.LDH Promoter::BPSI.5 Intron::GUS::NOS Terminator (pBPSLM229)

pBPSLM229 shows weak expression in endosperm and aleuron layer, mainlyat the top side of the kernel. No expression was detected in any othertissue tested.

What is claimed is:
 1. A recombinant DNA expression constructcomprising: a) at least one promoter sequence functioning in plants orplant cells; b) at least one intron comprising a sequence selected fromthe group consisting of the sequences of SEQ ID NOs: 3, 5, 6, 7, 10, 11,12, 13, 14, 15, 16, 17, 18, 19, 20, 21, and 22, and functionalequivalents thereof; and c) at least one nucleic acid sequence, whereinthe at least one promoter sequence and at least one intron arefunctionally linked to the at least one nucleic acid sequence, whereinthe at least one intron is heterologous to the at least one nucleic acidsequence and/or to the at least one promoter sequence, and wherein thefunctional equivalents thereof increase gene expression and comprise asequence having at least 80% sequence identity to the full-lengthsequence of SEQ ID NO: 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, or 22 and comprise I) an intron length shorter than 1000base pairs, and II) a 5′ splice site comprising the dinucleotidesequence 5′-GT-3′ (SEQ ID NO: 78), and III) a 3′ splice site comprisingthe trinucleotide sequence 5′-CAG-3′ (SEQ ID NO: 79), and IV) a branchpoint resembling the consensus sequence 5′-CURAY-3′ (SEQ ID NO: 75)upstream of the 3′ splice site.
 2. The recombinant DNA expressionconstruct of claim 1, wherein said nucleic acid encodes i) a protein orii) a sense, antisense, or double-stranded RNA sequence.
 3. Therecombinant DNA expression construct of claim 1, wherein said promotersequence functioning in plants or plant cells is selected from the groupconsisting of a) a promoter comprising nucleotides 1 to 854 of SEQ IDNO: 113, or a sequence having at least 95% identity to nucleotides 1 to854 of SEQ ID NO: 113, or a sequence comprising at least 300 consecutivenucleotides of SEQ ID NO: 113, b) a promoter comprising nucleotides 1 to1184 of SEQ ID NO: 114, or a sequence having at least 95% identity tonucleotides 1 to 1184 of SEQ ID NO: 114, or a sequence comprising atleast 300 consecutive nucleotides of SEQ ID NO: 114, c) a promotercomprising nucleotides 1 to 1034 of SEQ ID NO: 115, or a sequence havingat least 90% identity to nucleotides 1 to 1034 of SEQ ID NO: 115, or asequence comprising at least 200 consecutive nucleotides of SEQ ID NO:115, d) a promoter comprising nucleotides 1 to 1440 of SEQ ID NO: 116,or a sequence having at least 95% identity to nucleotides 1 to 1440 ofSEQ ID NO: 116, or a sequence comprising at least 300 consecutivenucleotides of SEQ ID NO: 116, e) a promoter comprising nucleotides 1 to1589 of SEQ ID NO: 117, or a sequence having at least 90% identity tonucleotides 1 to 1589 of SEQ ID NO: 117, or a sequence comprising atleast 200 consecutive nucleotides of SEQ ID NO: 117, f) a promotercomprising nucleotides 1 to 796 of SEQ ID NO: 118, or a sequence havingat least 95% identity to nucleotides 1 to 796 of SEQ ID NO: 118, or asequence comprising at least 300 consecutive nucleotides of SEQ ID NO:118, g) a promoter comprising nucleotides 1 to 1062 of SEQ ID NO: 119,or a sequence having at least 95% identity to nucleotides 1 to 1062 ofSEQ ID NO: 119, or a sequence comprising at least 300 consecutivenucleotides of SEQ ID NO: 119, and h) a promoter comprising nucleotides1 to 1386 of SEQ ID NO: 121, or a sequence having at least 95% identityto nucleotides 1 to 1386 of SEQ ID NO: 121, or a sequence comprising atleast 300 consecutive nucleotides of SEQ ID NO:
 121. 4. An expressionvector comprising the recombinant DNA expression construct of claim 1.5. A transgenic cell or transgenic non-human organism or a cell culture,part or propagation material derived therefrom comprising the expressionconstruct of claim 1 or a vector comprising the expression construct,wherein the cell or non-human organism is from a bacterium or plant. 6.The transgenic cell or non-human organism of claim 5, wherein said cellor organism is a monocotyledonous plant cell or organism selected fromthe group consisting of the genera Hordeum, Avena, Secale, Triticum,Sorghum, Zea, Saccharum, and Oryza.
 7. A method for providing anexpression cassette for enhanced expression of a nucleic acid sequencein a plant or a plant cell or for enhancing the expression of a nucleicacid sequence in a plant or a plant cell, comprising functionallylinking at least one intron as described in claim 1 to a nucleic acidsequence.
 8. The method of claim 7, wherein said nucleic acid sequenceencodes a selectable marker protein, a screenable marker protein, ananabolic active protein, a catabolic active protein, a biotic or abioticstress resistance protein, a male sterility protein, a protein affectingplant agronomic characteristics, or a sense, antisense, ordouble-stranded RNA.
 9. The recombinant DNA expression construct ofclaim 10, wherein the functional equivalents comprise i) an adenine plusthymine content of at least 40% over 100 nucleotides downstream from the5′ splice site, and ii) an adenine plus thymine content of at least 50%over 100 nucleotides upstream from the 3′ splice site, and iii) anadenine plus thymine content of at least 55%, and a thymine content ofat least 30% over the entire intron.
 10. The recombinant DNA expressionconstruct of claim 1, wherein the functional equivalents comprise asequence having at least 90% sequence identity to the full-lengthsequence of SEQ ID NO: 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18,19, 20, 21, or
 22. 11. The recombinant DNA expression construct of claim1, wherein the functional equivalents comprise a sequence having atleast 95% sequence identity to the full-length sequence of SEQ ID NO: 3,5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or
 22. 12. Therecombinant DNA expression construct of claim 1, wherein the at leastone intron comprises the sequence of SEQ ID NO: 3, 5, 6, 7, 10, 11, 12,13, 14, 15, 16, 17, 18, 19, 20, 21, or
 22. 13. The method of claim 7,wherein the functional equivalents comprise a sequence having at least95% sequence identity to the full-length sequence of SEQ ID NO: 3, 5, 6,7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, or
 22. 14. The methodof claim 7, wherein the at least one intron comprises the sequence ofSEQ ID NO: 3, 5, 6, 7, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21,or
 22. 15. The method of claim 7, further comprising linking a promoterfunctional in plants to the nucleic acid sequence.
 16. The method ofclaim 7 wherein the plant is a monocotyledonous plant or the plant cellis from a monocotyledonous plant.
 17. A method for producing atransgenic plant or plant cell comprising transforming a plant or plantcell with the recombinant DNA expression construct of claim 1, andoptionally regenerating a plant from the transformed plant cell.
 18. Themethod of claim 17, wherein the plant is a monocotyledonous plant or theplant cell is from a monocotyledonous plant.